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Sodium is a chemical element; it has symbol Na (from Neo-Latin natrium) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isotope is 23 Na. The free metal does not occur in nature and must be prepared from compounds.
For other isotopes, the isotopic mass is usually within 0.1 u of the mass number. For example, 35 Cl (17 protons and 18 neutrons) has a mass number of 35 and an isotopic mass of 34.96885. [7] The difference of the actual isotopic mass minus the mass number of an atom is known as the mass excess, [8] which for 35 Cl is –0.03115.
An example of use of a mass number is "carbon-12," which has 12 nucleons (six protons and six neutrons). The actual mass of an atom at rest is often expressed in daltons (Da), also called the unified atomic mass unit (u). This unit is defined as a twelfth of the mass of a free neutral atom of carbon-12, which is approximately 1.66 × 10 −27 ...
Sodium chloride / ˌ s oʊ d i ə m ˈ k l ɔːr aɪ d /, [8] commonly known as edible salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chlorine ions. It is transparent or translucent, brittle, hygroscopic , and occurs as the mineral halite .
Sodium-23 is an isotope of sodium with an atomic mass of 22.98976928. It is the only stable isotope of sodium and also the only primordial isotope. Because of its abundance, sodium-23 is used in nuclear magnetic resonance in various research fields, including materials science and battery research. [ 8 ]
The net charge of an ion is not zero because its total number of electrons is unequal to its total number of protons. A cation is a positively charged ion with fewer electrons than protons [2] (e.g. K + (potassium ion)) while an anion is a negatively charged ion with more electrons than protons. [3] (e.g. Cl − (chloride ion) and OH − ...
For example, the relative isotopic mass of a carbon-12 atom is exactly 12. For comparison, the atomic mass of a carbon-12 atom is exactly 12 daltons. Alternately, the atomic mass of a carbon-12 atom may be expressed in any other mass units: for example, the atomic mass of a carbon-12 atom is 1.992 646 882 70 (62) × 10 −26 kg.
Approximate definition of a mole based on 12 grams of carbon-12. The Avogadro constant was historically derived from the old definition of the mole as the amount of substance in 12 grams of carbon-12 (12 C); or, equivalently, the number of daltons in a gram, where the dalton is defined as 1 / 12 of the mass of a 12 C atom. [8]