Communication
Faster access than browser!

# Atomic number

In chemistry and physics, the atomic number of a chemical element (also known as its proton number) is the number of protons found in the nucleus of an atom of that element, and therefore identical to the charge number of the nucleus. [1]

## Antonius van den Broek

Antonius Johannes van den Broek (4 May 1870, Zoetermeer - 25 October 1926, Bilthoven) was a Dutch amateur physicist notable for being the first who realized that the number of an element in the periodic table (now called atomic number) corresponds to the charge of its atomic nucleus.

## Atom

An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element.

## Atomic mass

The atomic mass (ma) is the mass of an atomic particle, sub-atomic particle, or molecule.

## Atomic mass unit

The unified atomic mass unit (symbol: u) or dalton (symbol: Da) is the standard unit that is used for indicating mass on an atomic or molecular scale (atomic mass).

## Atomic nucleus

The nucleus is the small, dense region consisting of protons and neutrons at the center of an atom.

## Atomic number

In chemistry and physics, the atomic number of a chemical element (also known as its proton number) is the number of protons found in the nucleus of an atom of that element, and therefore identical to the charge number of the nucleus.

## Atomic theory

In chemistry and physics, atomic theory is a scientific theory of the nature of matter, which states that matter is composed of discrete units called atoms.

## Bohr model

In atomic physics, the Rutherford–Bohr model or Bohr model, introduced by Niels Bohr in 1913, depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus&mdash;similar in structure to the solar system, but with attraction provided by electrostatic forces rather than gravity.

## Charge number

Charge number or valence of an ion is the coefficient that, when multiplied by the elementary charge, gives the ion's charge.

## Chemical bond

A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms.

## Chemical element

A chemical element (or element) is a chemical substance consisting of atoms having the same number of protons in their atomic nuclei (i.e. the same atomic number, Z).

## Chemistry

Chemistry is a branch of physical science that studies the composition, structure, properties and change of matter.

## Dmitri Mendeleev

Dmitri Ivanovich Mendeleev (a; 8 February 1834 &ndash; 2 February 1907 O.S. 27 January 1834 &ndash; 20 January 1907) was a Russian chemist and inventor.

## Effective atomic number

Effective atomic number has two different meanings: one that is the effective nuclear charge of an atom, and one that calculates the average atomic number for a compound or mixture of materials.

## Electric charge

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field.

## Electron

The electron is a subatomic particle, symbol or, with a negative elementary electric charge.

## Electron configuration

In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals.

## Electron shell

In chemistry and atomic physics, an electron shell, or a principal energy level, may be thought of as an orbit followed by electrons around an atom's nucleus.

## Ernest Rutherford

Ernest Rutherford, 1st Baron Rutherford of Nelson, (30 August 1871 – 19 October 1937) was a New Zealand-born British physicist who became known as the father of nuclear physics.

## German language

German (Deutsch) is a West Germanic language that derives most of its vocabulary from the Germanic branch of the Indo-European language family.

## Hafnium

Hafnium is a chemical element with symbol Hf and atomic number 72.

## Half-life

Half-life (t1⁄2) is the amount of time required for the amount of something to fall to half its initial value.

## Henry Moseley

Henry Gwyn Jeffreys Moseley known as Harry Moseley (23 November 1887 – 10 August 1915) was an English physicist.

## History of the periodic table

The periodic table is an arrangement of the chemical elements, organized on the basis of their atomic numbers, electron configurations and recurring chemical properties.

## Hydrogen

Hydrogen is a chemical element with chemical symbol H and atomic number 1.

## Iodine

Iodine is a chemical element with symbol I and atomic number 53.

## Island of stability

In nuclear physics, the island of stability is the prediction that a set of heavy isotopes with a near magic number of protons and neutrons will temporarily reverse the trend of decreasing stability in elements heavier than Uranium.

## Isotope

Isotopes are variants of a particular chemical element which differ in neutron number, although all isotopes of a given element have the same number of protons in each atom.

Sir James Chadwick, (20 October 1891 – 24 July 1974) was an English physicist who was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron in 1932.

## Lanthanide

The lanthanide or lanthanoid series of chemical elements comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium.

## Lanthanum

Lanthanum is a soft, ductile, silvery-white metallic chemical element with symbol La and atomic number 57.

## Lutetium

Lutetium is a chemical element with symbol Lu and atomic number 71.

## Mass number

The mass number (A), also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus.

## Monoisotopic element

A monoisotopic element is one of 26 chemical elements which have only a single stable isotope (nuclide).

## Moseley's law

Moseley's law is an empirical law concerning the characteristic x-rays that are emitted by atoms.

## Natural number

In mathematics, the natural numbers (sometimes called the whole numbers): "whole number An integer, though sometimes it is taken to mean only non-negative integers, or just the positive integers." give definitions of "whole number" under several headwords: INTEGER … Syn. whole number.

## Neutron

The neutron is a subatomic particle, symbol or, with no net electric charge and a mass slightly larger than that of a proton.

## Neutron number

The neutron number, symbol N, is the number of neutrons in a nuclide.

## Nuclear reaction

In nuclear physics and nuclear chemistry, a nuclear reaction is semantically considered to be the process in which two nuclei, or else a nucleus of an atom and a subatomic particle (such as a proton, neutron, or high energy electron) from outside the atom, collide to produce one or more nuclides that are different from the nuclide(s) that began the process.

## Nucleon

In chemistry and physics, a nucleon is one of the particles that makes up the atomic nucleus.

## Periodic table

The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number (number of protons in the nucleus), electron configurations, and recurring chemical properties.

## Physics

Physics (from knowledge of nature, from φύσις phúsis "nature") is the natural science that involves the study of matterAt the start of The Feynman Lectures on Physics, Richard Feynman offers the atomic hypothesis as the single most prolific scientific concept: "If, in some cataclysm, all scientific knowledge were to be destroyed one sentence what statement would contain the most information in the fewest words? I believe it is that all things are made up of atoms – little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another..." and its motion through space and time, along with related concepts such as energy and force."Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of events." More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves."Physics is one of the most fundamental of the sciences. Scientists of all disciplines use the ideas of physics, including chemists who study the structure of molecules, paleontologists who try to reconstruct how dinosaurs walked, and climatologists who study how human activities affect the atmosphere and oceans. Physics is also the foundation of all engineering and technology. No engineer could design a flat-screen TV, an interplanetary spacecraft, or even a better mousetrap without first understanding the basic laws of physics. (...) You will come to see physics as a towering achievement of the human intellect in its quest to understand our world and ourselves."Physics is an experimental science. Physicists observe the phenomena of nature and try to find patterns that relate these phenomena.""Physics is the study of your world and the world and universe around you." Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy. Over the last two millennia, physics was a part of natural philosophy along with chemistry, certain branches of mathematics, and biology, but during the scientific revolution in the 17th century, the natural sciences emerged as unique research programs in their own right. Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry, and the boundaries of physics are not rigidly defined. New ideas in physics often explain the fundamental mechanisms of other sciences while opening new avenues of research in areas such as mathematics and philosophy. Physics also makes significant contributions through advances in new technologies that arise from theoretical breakthroughs. For example, advances in the understanding of electromagnetism or nuclear physics led directly to the development of new products that have dramatically transformed modern-day society, such as television, computers, domestic appliances, and nuclear weapons; advances in thermodynamics led to the development of industrialization, and advances in mechanics inspired the development of calculus.

## Proton

| magnetic_moment.

## Prout's hypothesis

Prout's hypothesis was an early 19th-century attempt to explain the existence of the various chemical elements through a hypothesis regarding the internal structure of the atom.

## Quantum mechanics

Quantum mechanics (QM; also known as quantum physics, or quantum theory), including quantum field theory, is a fundamental branch of physics concerned with processes involving, for example, atoms and photons.

## Relative atomic mass

Relative atomic mass (symbol: A) is a dimensionless physical quantity, the ratio of the average mass of atoms of an element (from a single given sample or source) to of the mass of an atom of carbon-12 (known as the unified atomic mass unit).

## Rutherford model

The Rutherford model is a model of the atom devised by Ernest Rutherford.

## Tellurium

Tellurium is a chemical element with symbol Te and atomic number 52.

## Thomas Royds

Thomas Royds (1884 - 1955) was a Solar physicist who worked with Ernest Rutherford on the identification of alpha radiation as the nucleus of the helium atom, and who was Director of the Kodaikanal Solar Observatory.

## X-ray tube

An X-ray tube is a vacuum tube that produces X-rays.

## References

Hey! We are on Facebook now! »