The document provides information about the history and development of the periodic table. It discusses how ancient Greeks like Empedocles believed that all matter was composed of four basic elements. It then outlines key contributions by Robert Boyle, Humphry Davy, Dobereiner, Newlands and Mendeleev to developing patterns in the properties of elements and early periodic table arrangements. Finally, it mentions Henry Moseley's discovery that atomic number, not mass, is the fundamental property determining an element's position in the periodic table.
1. The document discusses the development and importance of the periodic table of elements. It traces the periodic table back to Dobereiner's triads in 1817 and covers contributions by scientists like Newlands, Meyer, Mendeleev and Moseley that led to the modern periodic table.
2. The periodic table organizes elements into vertical columns called groups with similar properties and horizontal rows called periods. Elements are classified based on their atomic structure and properties like reactivity and atomic radius that vary periodically with atomic number.
3. The periodic table is useful for predicting chemical behaviors and properties of elements based on their location in the table. It provides an organized framework for understanding the relationships between elements and how their properties change
Science 8 Quarter 3 WEEK7 Periodic Table of Elements.pptxJaniceMukod1
The document discusses the key elements of the periodic table including atomic number, atomic mass, and how elements are arranged. It summarizes the contributions of Dmitri Mendeleev and Henry Moseley. Mendeleev arranged elements based on atomic mass and left gaps for undiscovered elements. Moseley discovered that atomic number is fundamental. The periodic table is arranged into periods and groups with metals, nonmetals and metalloids. Different groups of elements are discussed including alkali metals, alkaline earth metals, halogens, and noble gases. Examples are given of elements and their properties.
1. Early chemists attempted to classify elements based on similarities in their properties, including Dobereiner who grouped elements into triads and Newlands who arranged them in octaves based on increasing atomic mass. However, these classifications had limitations as they could not accommodate all known elements.
2. Mendeleev organized the periodic table with elements arranged in order of increasing atomic mass and proposed that elements with similar properties would fall into the same groups. His periodic table allowed for predictions of unknown elements and became widely accepted.
3. Modern periodic tables are based on atomic number rather than mass and include additional periodic trends like atomic size, metallic character, and valency that help explain elements' properties. The current 18-
1. Early chemists like Dobereiner and Newlands attempted to classify elements based on their properties, but their systems had limitations as they could not accommodate all known elements.
2. Mendeleev organized the known elements into the first periodic table based on their atomic masses and properties, allowing elements with similar properties to be grouped together. He also predicted new elements, and his table became the basis for modern classifications.
3. The modern periodic table is arranged by atomic number rather than atomic mass. Elements in the same group have the same number of valence electrons and similar properties, while periods correspond to the filling of electron shells as atomic number increases from left to right.
The document provides an overview of a 12-lesson chemistry course covering topics like the periodic table, alkaline metals, chemical equations, halogens, helium, atomic structure, electrons, salts, and ionic theory. It includes lesson objectives, activities, extension questions, and summaries for the first two lessons which focus on the periodic table and alkaline metals. Key points covered are the periodic table's arrangement of elements, properties of group 1 alkaline metals like their reactions with water and acids, and their similarities and reactivity trends.
1. The document summarizes the history and development of the periodic table, including contributions from Greek philosophers, Boyle, Davy, Moseley, Dobereiner, Newlands, and Mendeleev.
2. It describes the key features and organization of the modern periodic table, including periods, groups, atomic number, valence electrons, and trends in physical/chemical properties for different groups like alkali metals, alkaline earth metals, halogens, noble gases, and transition metals.
3. Specific elements are highlighted from different groups to illustrate trends, including lithium, sodium, potassium, beryllium, barium, calcium, magnesium, strontium, radium, chlorine, brom
01-VI_OLY_CHE_PERODIC CLASSIFICATION_VOL-4_PG-1 TO 45.pdfssuseree13e2
1. The document discusses various early attempts at classifying elements, including Dobereiner's classification of elements into triads based on their atomic masses and properties, Lavoisier's classification of elements as metals and non-metals, and Newlands' law of octaves.
2. Newlands noticed that when elements were arranged in order of increasing atomic mass, the eighth element had similar properties to the first element, analogous to the octave in music. This led to the idea of periodicity, where properties repeat at regular intervals.
3. The law of octaves was an important step towards recognizing a systematic relationship between the order of atomic masses and the periodic repetition of element properties, laying the foundation for
Strontium is a soft, silver-gray metal with symbol Sr and atomic number 38 that exists as four stable isotopes in nature, most dominantly strontium-88 which comprises 83% of natural strontium. It is found ubiquitously in minerals like celestite and strontianite, making up about 0.025% of the Earth's crust. While strontium has 16 radioactive isotopes, only strontium-90 has a sufficiently long half-life of 29 years to be of concern to human health.
During the 19th century, chemists began categorizing elements based on their properties, leading to modern periodic tables. Johann Dobereiner observed that some elements formed triads with similar properties. John Newlands proposed an early periodic law in which properties repeated every eighth element, though this failed with new discoveries. Dmitri Mendeleev and Lothar Meyer independently created early periodic tables arranging elements by atomic mass, with Mendeleev accurately predicting unknown elements. Henry Moseley determined elements' ordering by atomic number, establishing the modern periodic table.
Periodic calssification of elements ncert shashikumar b sghsykhalli
The document provides an overview of the periodic classification of elements. It discusses early attempts at classification including Dobereiner's triads and Newlands' law of octaves. It then covers Mendeleev's periodic table, including its merits and defects. Finally, it describes the modern periodic table based on atomic number, including periodic trends in properties like atomic size and electronegativity across periods and down groups. Key topics covered include the groups and periods in the modern table, how to read and understand its layout, and common questions about periodic trends and properties.
chemistry matter and changes the periodic tableAmelHanafi3
The periodic table evolved over time as scientists discovered more useful ways to organize the elements. John Newlands proposed arranging elements by atomic mass and noticed properties repeated every eighth element, known as the law of octaves. Meyer and Mendeleev connected atomic mass to properties and Mendeleev predicted undiscovered elements. Moseley rearranged the table by atomic number, resulting in the modern periodic table with periodic repetition of properties. The modern table contains element names, symbols, atomic numbers, and masses, arranged in groups and periods.
The document discusses the periodic table of elements, explaining how the elements are organized according to properties like atomic number and mass and describing important groups of elements including metals, non-metals, noble gases, and families like alkali metals and halogens. It provides details on the development of the periodic table and key aspects of classifying and understanding the elements.
The periodic table organizes the 118 known chemical elements according to their atomic structure and properties, with elements in the same columns having similar traits. Elements can exist individually, combine to form compounds with distinct properties, or be mixed together without bonding. The periodic table provides a framework for understanding elements and predicting how they will react and combine.
The periodic table is a chart that arranges the elements in rows and columns according to their physical and chemical properties. Elements in the same group have similar properties, and an element's location on the periodic table provides information about its properties. Metals are generally located on the left side and middle of the periodic table and have properties such as conductivity and luster, while nonmetals are usually gases or brittle solids found on the right side. Metalloids exhibit some properties of both metals and nonmetals.
The periodic table organizes elements based on their atomic structure and properties. It has evolved over time as new elements were discovered and scientists like Dobereiner, Newlands, Mendeleev, and Moseley developed patterns in properties and arranged elements in increasing order of atomic number. The modern periodic table is divided into blocks including alkali metals, alkaline earth metals, transition metals, and nonmetals. Each block contains groups of elements with similar properties due to their valence electrons. The periodic table is a fundamental tool for chemists.
The document provides information about the periodic table of elements, including that it organizes elements according to their atomic number and properties. Key aspects of the periodic table include the atomic number, atomic mass, symbols, and position of elements which can provide insight into their properties. The document also summarizes common elements, families of elements, and properties of metals, non-metals, and metalloids.
The periodic table evolved over time as scientists discovered more useful ways to organize the elements. Elements are organized into blocks according to their electron configurations, with trends in properties like atomic radius occurring from period to period and group to group. Atomic radius generally decreases left to right as nuclear charge increases, and increases down a group as the outer orbital size increases. Ionic radius follows similar trends but is smaller for positive ions and larger for negative ions due to electron gain or loss.
The document discusses the periodic table of elements created by Dmitri Mendeleev in 1869. It organizes all known elements based on their atomic structure and chemical properties. Key terms defined include atomic number, symbol, atomic weight, protons, electrons, neutrons, metals, non-metals, metalloids, periods, families, and properties of common element groups such as alkali metals, halogens and noble gases. The periodic table arranges elements horizontally by atomic number and vertically into families with similar traits.
The document discusses the periodic table and periodic trends in properties of elements. It defines key periodic table terms like groups, periods, atomic radius, ionization energy, and provides examples of how properties change within periods and groups. It also discusses Mendeleev's original periodic table and the modern periodic law.
periodic table of elements for grade 8 learnersAceReyes9
The document provides an overview of the periodic table of elements and key concepts related to elements and their organization. It discusses how elements are organized according to their atomic number and properties that can be determined from an element's position on the periodic table. Examples of different families of elements are provided, including their typical properties and valence electron configuration. Key terms like atomic number, atomic mass, and symbols are defined.
Similar to 1_the_periodic_table_for_website.ppt (20)
Newton's first law of motion states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. It describes the tendency of objects to resist any change in their state of motion. The document provides explanations of examples that illustrate Newton's first law, such as blood rushing to the feet when an elevator abruptly stops, or a person flying off a skateboard when it hits a rock. Galileo refined the concept of inertia, which is an object's resistance to changes in its motion.
HEALTH FACILITIES and Complementary.Alternative Healthcare ( LESSON 2 and 4)....Francis de Castro
The document discusses various topics related to healthcare facilities and providers. It begins by describing primary care providers and different types of nurses. It then outlines various medical specialties and specialists, including oncology, physical therapy, psychiatry, and urology. The document also discusses different types of healthcare facilities like hospitals, walk-in surgery centers, and extended care facilities. It provides details on hospitals, including private, voluntary, public, and teaching hospitals. It concludes by listing 10 herbs approved by the Department of Health for use in herbal medicine in the Philippines.
This document provides information for students preparing for a career in health care. It discusses the growth of health care careers and fastest growing occupations. The Career Center and Health Professions Coordinator at Gustavus Adolphus College help students explore options and prepare applications for medical, dental, nursing and other health programs. Students are advised to maintain strong grades, complete required coursework, and gain relevant experience through internships, volunteering, and shadowing professionals to become a competitive applicant for medical and other health programs.
Our planet is changing due to various factors that negatively impact the environment. However, there are many things individuals can do to help such as recycling, carpooling, riding bicycles, reducing food waste, avoiding plastics, proper waste disposal, planting trees, using less energy, and participating in community cleanups. Taking these actions helps conserve natural resources, reduces pollution, and maintains a greener environment for future generations.
The document discusses various coastal processes and how they shape shorelines. It defines key terms like longshore transport, cross-shore transport, erosion, deposition and landforms they can create. It also summarizes different models used to calculate rates of sediment transport alongshore and on-offshore, including the energy flux model. Measurement techniques for studying these dynamic coastal systems are outlined. The document emphasizes the importance of understanding coastal processes for applications like coastal development and protection.
Newton's first law of motion states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. It describes the tendency of objects to resist any change in their state of motion. The document provides explanations of examples that illustrate Newton's first law, such as blood rushing to the feet when an elevator abruptly stops, or a person flying off a skateboard when it hits a rock and stops suddenly. Galileo refined the concept of inertia, which is an object's resistance to changes in its motion.
The document discusses the importance of occupational health and safety (OHS) in the workplace. It outlines an employer's legal responsibilities to maintain a healthy and safe work environment. Implementing OHS practices can benefit a business by reducing injuries, improving productivity and employee retention, and lowering costs. The document provides tips for employers to comply with OHS laws such as providing a safe work environment, equipment, training, and facilities.
Volcanic eruptions occur when pressure builds up within a volcano, causing its molten rock to erupt violently. Eruptions can send lava, poisonous gases, ash, and rock over large distances. When a volcano erupts, its top may explode and fires will pour down its sides, endangering nearby life. Preparedness is key - learn evacuation plans, have emergency supplies, protect property from ash, and heed all warnings. The Philippine volcano Mount Mayon is one of the country's most active and dangerous due to its past eruptions which have buried towns and killed over 1,000 people.
Earwax is produced by the body to protect the ears, with lubricating and antibacterial properties. If earwax becomes impacted or hardened, it can lead to hearing loss, ear irritation, pain, dizziness, and ringing in the ears. Soft cloths should be used to clean the ears instead of cotton buds or other objects. Xerophthalmia is a medical condition caused by vitamin A deficiency where the eyes fail to produce tears, resulting in white spots and ulcers on the cornea. Eating foods rich in vitamin A can help prevent xerophthalmia. Strabismus, also known as crossed eyes, occurs when the eyes do not properly align when looking at an object,
Covalent bonding occurs when two nonmetal atoms share pairs of electrons to achieve stable octets. Atoms form covalent bonds by sharing electrons, depicted using Lewis dot structures. There are three main types of bonding: ionic, metallic, and covalent. Covalent bonding is the focus of this chapter and forms molecules by electron sharing between nonmetals.
The document summarizes information about constellations and how they appear to change positions in the night sky throughout the year. It discusses circumpolar constellations that never set below the horizon from a particular location, including the three main circumpolar constellations in the northern and southern hemispheres. It also describes the 12 zodiac constellations and the dates each is visible. The positions of constellations seen from Earth depend on the observer's latitude and the time of year.
The Milky Way Galaxy is a spiral galaxy that contains stars, dust, and gas. It has a disk shape with a central bulge and spherical halo. The galaxy contains spiral arms, globular clusters, and over 100 billion stars. While stars and gas account for only about 10% of the Milky Way's mass, the remaining 90% is made up of mysterious dark matter, which is only detectable through its gravitational effects. Understanding the nature of dark matter remains an important unsolved problem in astrophysics.
This document describes the evolution of cosmological models throughout history from ancient Earth-centered models to the current Big Bang model. It discusses how each new model was developed in response to new observations that could not be explained by existing models, from Copernicus developing the Sun-centered model to resolve issues with planetary retrograde motion to Hubble establishing the expanding universe model based on the observation of redshift in galaxies. The document also outlines how new discoveries like dark matter and dark energy have led to refinements of the Big Bang model but not a rejection of the overall framework. It emphasizes that science advances through an ongoing process of testing predictions made by models against observations.
Charles's law describes how gases tend to expand when heated. It states that when the pressure on a sample of a dry gas is held constant, the Kelvin temperature and volume will be directly related. Specifically, if the temperature is increased, the volume will also increase in direct proportion. The document provides examples of problems applying Charles's law formula to calculate new volumes given changes in temperature. It also gives real-life examples of how Charles's law applies, such as how hot air balloons and deodorant bottles work based on gas expansion with temperature changes.
This document summarizes key concepts related to orogenesis including folding, faulting, and volcanism. It describes three main types of faulting - normal, reverse/thrust, and transform/strike-slip. Examples of related landforms like horsts and grabens formed by normal faulting are provided. Transform faults like the San Andreas are described as forming shallow linear valleys with little volcanism. The earthquake cycle and seismic wave types are summarized. Historic earthquakes in California like the 1857 Fort Tejon and 1906 San Francisco quakes are overviewed. Finally, the document classifies volcanoes and provides examples of explosive composite cones and effusive shield volcanoes formed at hot spots.
1. The document describes celestial motions like the celestial sphere, equator, ecliptic, solstices, equinoxes, and constellations. It also discusses models of the universe from ancient Egyptians to Copernicus, including geocentric models of Pythagoras, Ptolemy, and Copernicus' heliocentric model.
2. The second part of the document covers Kepler's laws of planetary motion - that planets move in ellipses with the Sun at one focus, areas are swept in equal times, and the square of periods is proportional to the cube of distances. It also discusses problems applying Kepler's laws.
3. The document provides a concise overview of important concepts
elementary-activities-to-celebrate-us-science-fiction-day (1).pptxFrancis de Castro
This document provides information about stars and constellations. It begins with an opening prayer and then defines astronomy. It discusses the characteristics used to classify stars, including color, size, brightness, mass, and surface temperature. Red stars have the coolest temperatures while blue stars are hottest. Stars are mostly made of helium and hydrogen. Constellations are groups of stars that form imaginary patterns. Well-known constellations like Orion, Aquarius, and Cassiopeia are described. The document also discusses the pole star Polaris and how astronomers measure the distance to stars. In closing, it emphasizes that studying stars has helped humans navigate and track time.
The document discusses the different levels of healthcare:
1) Primary care involves general medical services and is usually the first point of contact.
2) Secondary care involves referrals to medical specialists for specific issues.
3) Tertiary care takes place in hospitals and requires advanced equipment and expertise for complex treatments.
4) Quaternary care is the most specialized level and includes experimental procedures. It is only offered by select hospitals.
The document discusses energy and the conservation of energy. It defines energy as the ability to do work and notes that it is measured in the same units as work. It then states the Law of Conservation of Energy - that energy cannot be created or destroyed, it can only be transferred or changed from one form to another, but the total quantity of energy remains the same. It provides examples of potential energy due to position in a force field, like gravity, and kinetic energy due to an object's motion. It shows how potential energy is transferred into kinetic energy for a freely falling body, demonstrating the conservation of energy.
The CGIAR needs a revolution John McIntire a, Achim Dobermann bAbdellah HAMMA
The CGIAR is a unique scientific organization that seeks to improve food security for low-income people. It
should be leading efforts to generate sustainable productivity gains in agriculture, especially in sub-Saharan
Africa where productivity lags. However, its current ill-adapted priorities and structure, its obsession with reorganizations,
and its unproductive ventures into local development projects have reduced its impact and
rendered it unable to respond to the challenge of food security under climate change. The system’s efforts have
become too diffuse and ineffective while attempts to revive impact through repeated re-organizations have
failed. The CGIAR has unique strengths: access to plant germplasm, know-how to improve germplasm and
agronomic practices, global networks of experimental sites and research collaborators, and excellent staff. The
CGIAR’s scientists are highly motivated, but leaders and funders of the system have failed to support them with a
simple, focused, and better funded operational environment needed to succeed in their research – and have
greater impact from it. This can be corrected. We propose a scientific and problem-driven focus on fewer global
and regional research priorities, supported by adequate long-term funding, rigorous methods of project evaluation,
and management that stimulates innovation and seeks verifiable results. These supports do not exist today
and we do not see that the current One CGIAR system will provide them in the foreseeable future.
We present the second data release (DR2) of the Far-Infrared Polarimetric Large-Area CMZ Exploration (FIREPLACE) survey. This survey utilized the Stratospheric Observatory for Infrared Astronomy (SOFIA) High-resolution Airborne Wideband Camera plus (HAWC+) instrument at 214 µm
(E-band) to observe dust polarization throughout the Central Molecular Zone (CMZ) of the Milky
Way. DR2 consists of observations that were obtained in 2022 covering the region of the CMZ extending roughly from the Brick to the Sgr C molecular clouds (corresponding to a roughly 1◦ × 0.75◦
region
of the sky). We combine DR2 with the first FIREPLACE data release covering the Sgr B2 region to
obtain full coverage of the CMZ (a 1.5◦ ×0.75◦
region of the sky). After applying total and polarized
intensity significance cuts on the full FIREPLACE data set we obtain ∼65,000 Nyquist-sampled polarization pseudovectors. The distribution of polarization pseudovectors confirms a bimodal distribution
in the CMZ magnetic field orientations, recovering field components that are oriented predominantly
parallel or perpendicular to the Galactic plane. These magnetic field orientations indicate possible
connections between the previously observed parallel and perpendicular distributions. We also inspect
the magnetic fields toward a set of prominent CMZ molecular clouds (the Brick, Three Little Pigs,
50 km s−1
, Circum-nuclear Disk, CO 0.02-0.02, 20 km s−1
, and Sgr C), revealing spatially varying
magnetic fields that generally trace the morphologies of the clouds. We find evidence that compression
from stellar winds and shear from tidal forces are prominent mechanisms influencing the structure of
the magnetic fields observed within the clouds.
How Does Simulation-Based Testing for Self-Driving Cars Match Human Perception?Christian Birchler
Software metrics such as coverage or mutation scores have been investigated for the automated quality assessment of test suites. While traditional tools rely on software metrics, the field of self-driving cars (SDCs) has primarily focused on simulation-based test case generation using quality metrics such as the out-of-bound (OOB) parameter to determine if a test case fails or passes. However, it remains unclear to what extent this quality metric aligns with the human perception of the safety and realism of SDCs. To address this (reality) gap, we conducted an empirical study involving 50 participants to investigate the factors that determine how humans perceive SDC test cases as safe, unsafe, realistic, or unrealistic. To this aim, we developed a framework leveraging virtual reality (VR) technologies, called SDC-Alabaster, to immerse the study participants into the virtual environment of SDC simulators. Our findings indicate that the human assessment of safety and realism of failing/passing test cases can vary based on different factors, such as the test’s complexity and the possibility of interacting with the SDC. Especially for the assessment of realism, the participants’ age leads to a different perception. This study highlights the need for more research on simulation testing quality metrics and the importance of human perception in evaluating SDCs.
This pdf is about the introduction to concept of Balanced Diet & Nutrients.
For more details visit on YouTube; @SELF-EXPLANATORY; https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
In recent years, the growth of scientific data and the increasing need for data sharing and collaboration in the field of environmental chemistry has led to the creation of various software and databases that facilitate research and development into the safety and toxicity of chemicals. The US-EPA Center for Computational Toxicology and Exposure has been developing software and databases that serve the chemistry community for many years. This presentation will focus on several web-based software applications which have been developed at the USEPA and made available to the community. While the primary software application from the Center is the CompTox Chemicals Dashboard which provides access to data for >1.2 million chemicals (https://comptox.epa.gov/dashboard), almost a dozen proof-of-concept applications have been built serving various capabilities. The publicly accessible proof-of-concept Cheminformatics Modules (https://www.epa.gov/chemicalresearch/cheminformatics) provides access to multiple applications in development allowing for hazard comparison for sets of chemicals, structure-substructure-similarity searching, structure alerts and batch QSAR prediction of both physicochemical and toxicity endpoints. A number of other applications, presently in development but not publicly accessible will also be discussed. These include AMOS, the database of Analytical Methods and Open Spectra.
Analytical methods can vary in nature from detailed regulatory methods to more summary in nature. Regulatory method documents can include details of analytes which can be studied, supported matrices, reagents, methodological details, statistical performance, interlaboratory validation and other details. Summary methods provide a general overview of reagents, instrumentation and commonly a short list of analytes. Regulatory bodies including the US Environmental Protection Agency (US-EPA), US Geological Survey (USGS), US Department of Agriculture (USDA) and others provide detailed analytical methods and collections of summary methods from the agrochemical industry, such as the US-EPA Environmental Chemistry Methods (https://www.epa.gov/pesticide-analytical-methods/environmental-chemistry-methods-ecm). Instrument vendors also provide access to many hundreds of application notes which can be considered as summary methods. AMOS presently contains >4,500 methods integrated to their chemical structures and > 230,000 public domain mass spectral data. AMOS allows for filtering of methods based on analyte, chemical class, method source and other related metadata. AMOS is an important facet of the developing Non-Targeted Analysis WebApp presently also in development at the EPA.
This presentation will provide an overview of existing publicly accessible Dashboards and work in progress to support analysis of pesticides, veterinary drug residues, and other chemicals in food, animal feed, and environmental samples.
A NICER VIEW OF THE NEAREST AND BRIGHTEST MILLISECOND PULSAR: PSR J0437−4715Sérgio Sacani
We report Bayesian inference of the mass, radius and hot X-ray emitting region properties - using data
from the Neutron Star Interior Composition ExploreR (NICER) - for the brightest rotation-powered
millisecond X-ray pulsar PSR J0437−4715. Our modeling is conditional on informative tight priors
on mass, distance and binary inclination obtained from radio pulsar timing using the Parkes Pulsar
Timing Array (PPTA) (Reardon et al. 2024), and we use NICER background models to constrain
the non-source background, cross-checking with data from XMM-Newton. We assume two distinct
hot emitting regions, and various parameterized hot region geometries that are defined in terms of
overlapping circles; while simplified, these capture many of the possibilities suggested by detailed
modeling of return current heating. For the preferred model identified by our analysis we infer a mass
of M = 1.418 ± 0.037 M⊙ (largely informed by the PPTA mass prior) and an equatorial radius of
R = 11.36+0.95
−0.63 km, each reported as the posterior credible interval bounded by the 16% and 84%
quantiles. This radius favors softer dense matter equations of state and is highly consistent with
constraints derived from gravitational wave measurements of neutron star binary mergers. The hot
regions are inferred to be non-antipodal, and hence inconsistent with a pure centered dipole magnetic
field.
No black holes from light einstein general relativitySérgio Sacani
— One of the consequences of the fact
that energy—and not mass—is the one responsible for
the curvature of spacetime is the a priori possibility
of having massless fields being held together by gravity. These exotic structures (known as geons) were first
considered by Wheeler [1–3] for electromagnetic fields.
The cases of the (almost massless) neutrinos [4] and the
gravitational field itself [5, 6] were subsequently studied.
These objects are found to be unstable under perturbations [7], leading to either a “leakage” of the massless
field [1] or its collapse into a black hole [8]. In this context, the term kugelblitz (German for “ball lightning”)
has become popular as a way to refer to any hypothetical black hole formed by the gravitational collapse of
electromagnetic radiation [9].
Kugelblitze are allowed by general relativity: there are
exact solutions to Einstein-Maxwell equations describing
black holes generated by the collapse of electromagnetic
energy [10, 11]. Kugelblitze have been studied in the
context of the cosmic censorship hypothesis [11–13], the
evaporation of white holes [11], dark matter [14], and
have even been proposed as the engine of a really speculative option for interstellar travel [15–17]. However, none
of these works take into account quantum effects, which
should play an important role in determining whether a
kugelblitz can form or not. This is especially so if we
are interested in black holes of small sizes such as the
artificial ones required in [15–17].
2. You should know the following by the end of
today’s class…
• History of the idea of elements including
the contributions of the Greeks, Boyle and
Davy and Moseley
• Symbols of elements 1–36.
• History of the periodic table, including the
contributions of Dobereiner and Newlands
• The differences between the first Periodic
table and the modern table
11. In particular Empedocles 490 – 435 BCE,
had the idea that there were four basic
building blocks (elements) from which
everything was made:
earth,
fire,
water
and air
The Ancient Greeks
IDEA THAT MATTER IS COMPOSED OF ELEMENTS AND THAT
DIFFERENT ELEMENTS COMBINE TO MAKE NEW THINGS!
12. The Ancient Greeks
Democritus
Around 2500 years ago
Piece of matter
Split or break up
Eventually I end up with something which
cannot be broken up – called an element
13. Robert Boyle
Robert Boyle
17th Century
Irish scientist,
Robert Boyle,
later defined what
an element was:
An element is a substance that cannot
be broken down into any simpler substance
Definition
14. Humphrey Davy
• Davy was an English chemist who started out
his research examining the medicinal effect of
various gases
18. Naming the elements
• After a planet ….mercury, uranium
• European mythological figures….Titanium after
the Titans
• After its colour…. Gold
• After a physical property… Bromine= bad smell
• After a country…. francium = France
• After yourself….?
• After a scientist… Es = Einsteinium
20. Recap
• What is an element?
• What did the ancient Greeks think
materials were made of?
• Who was Robert Boyle?
• What contribution did Davy make to the
knowledge of the elements?
22. Arrangement of the elements
•All of the known elements
of today are arranged on
….The Periodic Table of
Elements
24. Looking for a pattern in the
elements
• In the 1800s over 50
elements had been
discovered and more
were being found!
• Chemists wanted to
find if there was any
pattern to the elements
Date of Discovery
25. Johann Dobereiner
Dobereiner
1829 – His theory of triads
He noticed that certain
elements in groups of 3
had similar physical &
chemical properties with
the atomic weight of the
middle element being
halfway between the other
two.
He called such a group of
elements a triad.
What contribution did Dobereiner make to the systematic arrangement of the elements? (6)
2005 Q. 4 (d) (6)
26. Newlands -1864
Newland arranged all of the known
elements in order of increasing
atomic weight and he noticed the
chemical and physical properties of
the elements repeated with every 8th
element.
Higher level only
27. John Newlands
Newlands
Law of octaves
H Li Be B C N O
F Na Mg Al Si P S
He arranged the elements in order of
increasing atomic weight
Every 8th known element had similar
physical & chemical properties.
John Newlands
What contribution did Newlands make to the systematic arrangement of the elements known to him? (6)
2006 Q. 4 (f) (6)
28. Newlands Octaves
• The problem is that after Calcium the pattern starts to
break down.
• Although Newland had the right idea, some of the
elements hadn’t been discovered yet and this caused
elements to be forced into the wrong group!
Higher level only
29. Mendeleev and the periodic
table
Mendeleev created the first periodic table by grouping
together elements in a certain way.
30. Dmitri Mendeleev
Mendeleev
1869 – He drew up the first
periodic table of the known
elements of his time by arranging
the elements in order of
increasing atomic weight.
He noticed repeating patterns
which lead him to make very
accurate predictions about
undiscovered elements.
33. The differences in Mendeleev’s table and
the modern periodic table
1. Mendeleev’s table was arranged in order of
increasing atomic mass. Modern table is
arranged in order of increasing atomic
number.
2. In Mendeleev’s table the noble gases are
not included in the modern Table they are.
3. There are gaps in Medeleev’s table but
there are none in the modern periodic table
as they have been discovered..
State two ways in which Mendeleev’s periodic table of the elements differs from that of Moseley.
2003 Q. 4 (i) (6)
36. What have you learnt about..
Dobereiner
Newlands
Mendeleev
Octaves
Triads
37. Henry Moseley
Moseley
1913 – Henry Moseley discovered
that the positive charge in the
nucleus of an atom of any element is
of a definite amount.
These units of positive charge
became known as protons. The
periodic table is now arranged in
order of increasing atomic number.
The atomic number of and element is the number of protons
in the nucleus of an atom of that element
Definition
2008 Q. 4 (b) (6)
What contribution did Henry Moseley, the scientist shown in the photograph, make to the systematic arrangement
of the elements in the periodic table?
43. Group 1 – The Alkali Metals
2. They all float on water
1. They are all shiny
metals which are easily
cut with a knife.
3. They are all extremely
reactive and have to be
stored in oil to prevent
them from reacting
with the oxygen in the
air.
44. Demonstration – The reaction of
the alkali metals with water
1 – The reaction of lithium with water
2 – The reaction of sodium with water
3 – The reaction of potassium with
water
45. Why do the alkali metals increase in
reactivity as you go down the group?
As you go down the group the atomic radius
increases and the outermost electron is much
further from the nucleus and is under less of an
effect so that element is more reactive. This
outer electron is also protected from the nucleus
by an inner ‘screening effect’ of the inner
electrons.
Lithium Sodium
Potassium
6
2006 Q. 5 (b) (9)
Explain, in terms of the structures of the atoms, the trend in reactivity down Group I (the alkali metal group) of the
periodic table.
46. Balanced Equations
Li
Lithium
½
+ H2O H2 + LiOH
Water Hydrogen
Lithium
Hydroxide
2 2 2
Na
Sodium
½
+ H2O H2 + NaOH
Water Hydrogen
Sodium
Hydroxide
2 2 2
K
Potassium
½
+ H2O H2 + KOH
Water Hydrogen
Potassium
Hydroxide
2 2 2
47. Check if you have learnt..
• What group 1 in the Table is called?
• How many electrons are in the outer shell
of group 1 elements?
• Some properties of group 1 metals?
• What happens when they are reacted with
water?
• What is the reactivity trend as you go
down the group?
48. In today’s class
• We will look at the properties of the rest of
the groups in the Periodic table.
49. Group 2 – The earth alkali metals
Includes the following elements:
Beryllium (Be)
Magnesium (Mg)
Calcium (Ca) and others!
•They are all metals
•All of the elements in group one have two electrons in their outermost
shell!
•They are reactive- They have a tendency when reacting with outer
elements to lose these outer electrons and form ionic compounds
•They react less vigorously with water to produce hydrogen
50. Group 2 – The Alkaline Earth Metals
2. They are reactive but
not as reactive as the
alkali metals
1. They all have 2
electrons in their outer
shell
51. Groups 3 -11 The d block metals
They are all metals and are
usually brightly coloured and
act as catalysts for chemical
reactions
Includes the following
elements:
Scandium (Sc)
Titanium (Ti)
Vanadium (V)
Chromium (Cr)
Manganese (Mn)
Iron (Fe)
Cobalt (Co)
Nickel (Ni)
Copper (Co)
Zinc (Zn) and others!
55. Group 16
•All have 6 electrons on their outermost shell!
•All of the group are metals except for Polonium which is a metal
56. Group 17 - The Halogens
•They are non metals
•All of the elements in group one
have seven electrons in their
outermost shell!
•They are reactive - They have a
tendency when reacting with
outer compounds to gain one
electron
58. Group 18 - The Noble gases
They are all non metals
They are all odourless
and colourless gases
They are very
unreactive as they have
an outer shell full of
electrons, which makes
them chemically stable