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The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number (represented by the symbol Z). Since each element is identified by the number of protons in its nucleus, each element has its own atomic number, which determines the number of atomic electrons and consequently the chemical ...
The mass number (symbol A, from the German word: Atomgewicht, "atomic weight"), [1] also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is approximately equal to the atomic (also known as isotopic) mass of the atom expressed in atomic mass units.
The chemical elements are distinguished from each other by the number of protons that are in their atoms. For example, any atom that contains 11 protons is sodium, and any atom that contains 29 protons is copper. Atoms with the same number of protons but a different number of neutrons are called isotopes of the same element.
The electron configuration is determined by the charge of the nucleus, which is determined by the number of protons, or atomic number. The number of neutrons is the neutron number. Neutrons do not affect the electron configuration. Atoms of a chemical element that differ only in neutron number are called isotopes.
Abundance of elements in Earth's crust per million Si atoms (y axis is logarithmic); the Oddo–Harkins rule is visible for most of the metallic elements.. All atoms heavier than hydrogen are formed in stars or supernovae through nucleosynthesis, when gravity, temperature and pressure reach levels high enough to fuse protons and neutrons together.
All atomic nuclei are composed of protons and neutrons bound together by the nuclear force.There are 286 primordial nuclides that occur naturally on earth, each corresponding to a unique number of protons, called the atomic number, Z, and a unique number of neutrons, called the neutron number, N.
where A = Atomic mass number (the number of protons Z, plus the number of neutrons N) and r 0 = 1.25 fm = 1.25 × 10 −15 m. In this equation, the "constant" r 0 varies by 0.2 fm, depending on the nucleus in question, but this is less than 20% change from a constant. [20]
Each chemical element has a unique atomic number (Z— for "Zahl", German for "number") representing the number of protons in its nucleus. [4] Each distinct atomic number therefore corresponds to a class of atom: these classes are called the chemical elements. [5] The chemical elements are what the periodic table classifies and organizes.