Periodic table and Related Topics

Chemical element

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Species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species.

$Estimated distribution of dark matter and dark energy in the universe. Only the fraction of the mass and energy in the universe labeled "atoms" is composed of chemical elements.$

Periodic table showing the cosmogenic origin of each element in the Big Bang, or in large or small stars. Small stars can produce certain elements up to sulfur, by the alpha process. Supernovae are needed to produce "heavy" elements (those beyond iron and nickel) rapidly by neutron buildup, in the r-process. Certain large stars slowly produce other elements heavier than iron, in the s-process; these may then be blown into space in the off-gassing of planetary nebulae

Abundances of the chemical elements in the Solar System. Hydrogen and helium are most common, from the Big Bang. The next three elements (Li, Be, B) are rare because they are poorly synthesized in the Big Bang and also in stars. The two general trends in the remaining stellar-produced elements are: (1) an alternation of abundance in elements as they have even or odd atomic numbers (the Oddo-Harkins rule), and (2) a general decrease in abundance as elements become heavier. Iron is especially common because it represents the minimum energy nuclide that can be made by fusion of helium in supernovae.

Mendeleev's 1869 periodic table: An experiment on a system of elements. Based on their atomic weights and chemical similarities.

Much of the modern understanding of elements developed from the work of Dmitri Mendeleev, a Russian chemist who published the first recognizable periodic table in 1869.

Metal

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Material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well.

A metal in the form of a gravy boat made from stainless steel, an alloy largely composed of iron, carbon, and chromium

A metal rod with a hot-worked eyelet. Hot-working exploits the capacity of metal to be plastically deformed.

Samples of babbitt metal, an alloy of tin, antimony, and copper, used in bearings to reduce friction

A sculpture cast in nickel silver—an alloy of copper, nickel, and zinc that looks like silver

Rhodium, a noble metal, shown here as 1 g of powder, a 1 g pressed cylinder, and a 1 g pellet

A sample of diaspore, an aluminum oxide hydroxide mineral, α-AlO(OH)

A neodymium compound alloy magnet of composition Nd2Fe14B on a nickel-iron bracket from a computer hard drive

A pile of compacted steel scraps, ready for recycling

The Artemision Bronze showing either Poseidon or Zeus, c. 460 BCE, National Archaeological Museum, Athens. The figure is more than 2 m in height.

A disc of highly enriched uranium that was recovered from scrap processed at the Y-12 National Security Complex, in Oak Ridge, Tennessee

White-hot steel pours like water from a 35-ton electric furnace, at the Allegheny Ludlum Steel Corporation, in Brackenridge, Pennsylvania.

A Ho-Mg-Zn icosahedral quasicrystal formed as a pentagonal dodecahedron, the dual of the icosahedron

Body-centered cubic crystal structure, with a 2-atom unit cell, as found in e.g. chromium, iron, and tungsten

Face-centered cubic crystal structure, with a 4-atom unit cell, as found in e.g. aluminum, copper, and gold

Hexagonal close-packed crystal structure, with a 6-atom unit cell, as found in e.g. titanium, cobalt, and zinc

Niobium crystals and a 1 cm{{sup|3}} anodized niobium cube for comparison

Molybdenum crystals and a 1 cm{{sup|3}} molybdenum cube for comparison

Tantalum single crystal, some crystalline fragments, and a 1 cm{{sup|3}} tantalum cube for comparison

Tungsten rods with evaporated crystals, partially oxidized with colorful tarnish, and a 1 cm{{sup|3}} tungsten cube for comparison

alt=Three, dark broccoli shaped clumps of oxidised lead with grossly distended buds, and a cube of lead which has a dull silvery appearance.| oxidised lead

alt=A silvery molasses-like liquid being poured into a circular container with a height equivalent to a smaller coin on its edge| Mercury being

Electrum, a natural alloy of silver and gold, was often used for making coins. Shown is the Roman god Apollo, and on the obverse, a Delphi tripod (circa 310–305 BCE).

A plate made of pewter, an alloy of 85–99% tin and (usually) copper. Pewter was first used around the beginning of the Bronze Age in the Near East.

A pectoral (ornamental breastplate) made of tumbaga, an alloy of gold and copper

Arsenic, sealed in a container to prevent tarnishing

Bismuth in crystalline form, with a very thin oxidation layer, and a 1 cm{{sup|3}} bismuth cube

Potassium pearls under paraffin oil. Size of the largest pearl is 0.5 cm.

Aluminum chunk, 2.6 grams, {{nowrap|1=1 x 2 cm}}

Scandium, including a 1 cm{{sup|3}} cube

Lutetium, including a 1 cm{{sup|3}} cube

Around 95 of the 118 elements in the periodic table are metals (or are likely to be such).

The three naturally-occurring isotopes of hydrogen. The fact that each isotope has one proton makes them all variants of hydrogen: the identity of the isotope is given by the number of protons and neutrons. From left to right, the isotopes are protium (1H) with zero neutrons, deuterium (2H) with one neutron, and tritium (3H) with two neutrons.

Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) due to different numbers of neutrons in their nuclei.

Electron configuration

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Distribution of electrons of an atom or molecule in atomic or molecular orbitals.

The approximate order of filling of atomic orbitals, following the arrows from 1s to 7p. (After 7p the order includes subshells outside the range of the diagram, starting with 8s.)

Electron configuration table showing blocks.

Knowledge of the electron configuration of different atoms is useful in understanding the structure of the periodic table of elements.

Blocks s, f, d, and p in the periodic table

Block (periodic table)

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A block of the periodic table is a set of elements unified by the atomic orbitals their valence electrons or vacancies lie in.

Atom

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Smallest unit of ordinary matter that forms a chemical element.

The Geiger–Marsden experiment:
Left: Expected results: alpha particles passing through the plum pudding model of the atom with negligible deflection.
Right: Observed results: a small portion of the particles were deflected by the concentrated positive charge of the nucleus.

The Bohr model of the atom, with an electron making instantaneous "quantum leaps" from one orbit to another with gain or loss of energy. This model of electrons in orbits is obsolete.

The binding energy needed for a nucleon to escape the nucleus, for various isotopes

A potential well, showing, according to classical mechanics, the minimum energy V(x) needed to reach each position x. Classically, a particle with energy E is constrained to a range of positions between x1 and x2.

3D views of some hydrogen-like atomic orbitals showing probability density and phase (g orbitals and higher are not shown)

This diagram shows the half-life (T½) of various isotopes with Z protons and N neutrons.

These electron's energy levels (not to scale) are sufficient for ground states of atoms up to cadmium (5s2 4d10) inclusively. Do not forget that even the top of the diagram is lower than an unbound electron state.

An example of absorption lines in a spectrum

Graphic illustrating the formation of a Bose–Einstein condensate

Scanning tunneling microscope image showing the individual atoms making up this gold (100) surface. The surface atoms deviate from the bulk crystal structure and arrange in columns several atoms wide with pits between them (See surface reconstruction).

Periodic table showing the origin of each element. Elements from carbon up to sulfur may be made in small stars by the alpha process. Elements beyond iron are made in large stars with slow neutron capture (s-process). Elements heavier than iron may be made in neutron star mergers or supernovae after the r-process.

While experimenting with the products of radioactive decay, in 1913 radiochemist Frederick Soddy discovered that there appeared to be more than one type of atom at each position on the periodic table.

Periodic table highlighting the first row of each block. Helium (He), as a noble gas, is normally shown over neon (Ne) with the rest of the noble gases. The elements within scope of this article are inside the thick black borders. The status of oganesson (Og, element 118) is not yet known.

Nonmetal

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[[File:Nonmetals in the periodic table.png|thumb|upright=0.85|

Electronegativity values of the group 16 chalcogen elements showing a W-shaped alternation or secondary periodicity going down the group

Modern periodic table extract showing nonmetal subclasses.
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† moderately strong oxidising agent
‡ strong oxidising agent

A small (about 2 cm long) piece of rapidly melting argon ice

A cluster of purple fluorite, a fluorine mineral, between two quartzes

Selenium conducts electricity around 1,000 times better when light falls on it, a property used since the mid-1870s in light-sensing applications.

A crystal of realgar, also known as "ruby sulphur" or "ruby of arsenic", an arsenic sulfide mineral As4S4

Brownish crystals of buckminsterfullerene С60, a semiconducting allotrope of carbon

Germanium occurs in some zinc-copper-lead ore bodies, in quantities sufficient to justify extraction. The pure form costs $360 per 100 grams, as at February 2022.

Extract of periodic table showing how often each element is classified as a nonmetal:

Glenn T. Seaborg

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American chemist whose involvement in the synthesis, discovery and investigation of ten transuranium elements earned him a share of the 1951 Nobel Prize in Chemistry.

Seaborg in 1950, with the ion exchanger elution column of actinide elements.

Seaborg (second from left) during Operation Plumbbob

From left to right: Chairman Seaborg, President Kennedy, Secretary McNamara on March 23, 1962. By this point, McNamara and Seaborg had been discussing the AEC's studies on the ecological effects of nuclear war and "clean" weapon alternatives. (Courtesy: National Security Archive, Original: National Archives)

President Kennedy and his Atomic Energy Commission Chairman, Glenn Seaborg

Seaborg (right) with marine biologist Dixy Lee Ray on September 17, 1968

Helen and Glenn Seaborg in Stockholm in 1951

His work in this area also led to his development of the actinide concept and the arrangement of the actinide series in the periodic table of the elements.