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The atomic mass ( ma or m) is the mass of an atom. Although the SI unit of mass is the kilogram (symbol: kg), atomic mass is often expressed in the non-SI unit dalton (symbol: Da) – equivalently, unified atomic mass unit (u). 1 Da is defined as 1⁄12 of the mass of a free carbon-12 atom at rest in its ground state. [ 1]
The dalton or unified atomic mass unit (symbols: Da or u) is a unit of mass defined as 1 12 of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest. [ 1][ 2] It is a non-SI unit accepted for use with SI. The atomic mass constant, denoted mu, is defined identically, giving mu = 1 12 ...
The periodic table is a tabular arrangement of the chemical elements, organized by their atomic number, electron configuration, and chemical properties. It is a useful tool for understanding the patterns and trends of the elements and their interactions. Learn more about the history, structure, and significance of the periodic table on Wikipedia.
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 number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number. For example, carbon-12, carbon-13, and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13, and 14, respectively. The atomic number of carbon is 6, which means that ...
This number was chosen so that if an element has an atomic mass of 1 u, a mole of atoms of that element has a mass close to one gram. Because of the definition of the unified atomic mass unit, each carbon-12 atom has an atomic mass of exactly 12 Da, and so a mole of carbon-12 atoms weighs exactly 0.012 kg. [61]
Atomic number is the number of protons, and therefore also the total positive charge, in the atomic nucleus. The Rutherford–Bohr model of the hydrogen atom ( Z = 1) or a hydrogen-like ion ( Z > 1 ). In this model, it is an essential feature that the photon energy (or frequency) of the electromagnetic radiation emitted (shown) when an electron ...
Potassium is a chemical element; it has symbol K (from Neo-Latin kalium) and atomic number 19. It is a silvery white metal that is soft enough to easily cut with a knife. [ 8] Potassium metal reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure.