Mass Number | Definition, Use, Properties, Examples

what is mass number

Definition of Mass Number The 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 and neutrons (together known as nucleons) in an atomic nucleus. It is approximately equal to the atom’s atomic (also known as isotopic) mass expressed in … Read more

Atomic Number | Discovery, Formula, History, Properties

atomic number

Definitions of Atomic Number In the symbol representing a particular nuclear or atomic species, the atomic number may be indicated as a left subscript. Atoms of each element contain a characteristic number of protons. In fact, the number of protons determines what atom we are looking at (e.g., all atoms with six protons are carbon … Read more

What is Molecular Mass | Definition, Formula, Examples

molecular mass

Definition of Molecular Mass The molecular mass (m) is the mass of a given molecule. It is measured in Daltons (Da or u). Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element. The related quantity relative molecular mass, as defined by IUPAC, is the ratio … Read more

Average Atomic Mass | Definition, History, Examples

average atomic mass

Definition of Average Atomic Mass Average atomic mass considers the isotopic abundance (relative to each other found in the Earth). For example, the most abundant carbon isotope is carbon-12, which has a relative abundance of 98.89%. The atomic masses of carbon-13 and carbon-14 are 13.003 amu and 14.003 amu, respectively. The average atomic mass of … Read more