- Physical Sciences
horizontal rows of elements in the periodic table that are arranged according to their atomic mass.
the nucleus of the new isotope that is formed as a result of radioactive decay.
usually metal atoms that lose electrons and become positive ions.
a group of elements that are non-reactive, monatomic gases (Group 0, 8 or 18).
the sum of the number of protons and neutrons (the nucleons) in the nucleus of an atom. It...