The atomic number or nuclear charge number (symbol Z) of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of...

mass number (symbol A, from the German word: Atomgewicht, "atomic weight"), also called atomic mass number or nucleon number, is the total number of protons...

is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). The definitive visualisation of...

lowest mass) has an atomic weight of 1.007825 Da. The value of this number is called the atomic mass. A given atom has an atomic mass approximately equal...

its mass number. The relative isotopic mass (see section below) can be obtained by dividing the atomic mass ma of an isotope by the atomic mass constant...

(or nuclides) of the same chemical element. They have the same atomic number (number of protons in their nuclei) and position in the periodic table (and...

and organizes. Hydrogen is the element with atomic number 1; helium, atomic number 2; lithium, atomic number 3; and so on. Each of these names can be further...

Hydrogen is a chemical element; it has symbol H and atomic number 1. It is the lightest and most abundant chemical element in the universe, constituting...

) is a chemical element; it has symbol Pb (from Latin plumbum) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead...

chemical element; it has chemical symbol Au (from Latin aurum) and atomic number 79. In its pure form, it is a bright, slightly orange-yellow, dense...

have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen...

(from Latin carbo 'coal') is a chemical element; it has symbol C and atomic number 6. It is nonmetallic and tetravalent—meaning that its atoms are able...

Nitrogen is a chemical element; it has symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table...

Oxygen is a chemical element; it has symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal...

Beryllium is a chemical element; it has symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal...

atomic number, denoted by Zeff, may refer to: Effective nuclear charge of an individual atom, as felt by electrons within that atom Effective atomic number...

Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous...

especially difficult to measure accurately. Graphs of abundance against atomic number can reveal patterns relating abundance to stellar nucleosynthesis and...

Neon is a chemical element; it has symbol Ne and atomic number 10. It is the second noble gas in the periodic table. Neon is a colorless, odorless, inert...

which had the temporary name of unniloctium, based on the digits of its atomic number. There are also some historical symbols that are no longer officially...

λίθος, líthos, 'stone') is a chemical element; it has symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions...

romanized: helios, lit. 'sun') is a chemical element; it has symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert, monatomic gas and...

Atomic theory is the scientific theory that matter is composed of particles called atoms. The definition of the word "atom" has changed over the years...

Fluorine is a chemical element; it has symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as pale yellow diatomic...

In quantum mechanics, an atomic orbital (/ˈɔːrbɪtəl/ ) is a function describing the location and wave-like behavior of an electron in an atom. This function...

discovered, the atomic masses had been determined to be (approximately) integer multiples of the mass of the hydrogen atom, and the atomic number had been identified...

Nihonium is a synthetic chemical element; it has symbol Nh and atomic number 113. It is extremely radioactive: its most stable known isotope, nihonium-286...

beyond those currently known and proven. The element with the highest atomic number known is oganesson (Z = 118), which completes the seventh period (row)...

The atomic radius of a chemical element is a measure of the size of its atom, usually the mean or typical distance from the center of the nucleus to the...

disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei...