Atomic mass units (amu)
Atomic mass units (amu)A unit of mass defined as the mass of a carbon-12 atom; approximately equal to the mass of
one proton or one neutron.
Atomic number
Atomic number
The number of protons in a given element.Atomic orbital
Atomic orbital
The region of space around the nucleus in an atom in which there is a high probability of finding
the electron.
Atomic radius
Atomic radius
The radius of an atom. The average distance between a nucleus and the outermost electron.
Usually measured as one-half the distance between two nuclei of an element in its elemental form.
Aufbau principle
Aufbau principle
The principle that electrons fill energy levels in a given atom in order of increasing energy,
completely filling one sublevel before beginning to fill the next.
Avogadro’s number
Avogadro’s number
The number corresponding to a mole. It is the number of carbon-12 atoms in exactly 12 g of