Vocab 2 vocab dkrause published on October 31, 2010 Stacked 1/10 The sum of the protons and neutrons in the nucleus of an atom proton electron mass number 2/10 when the properties of the elements repeat in each period or row of the table group atomic mass periodic table 3/10 The smallest particle of and element element atom energy level 4/10 the tables vertical columns groups periodic table chemical symbol 5/10 an element that lacks most of the properties of a metal diatomic molecule nonmetal halogens 6/10 the spontaneous emersion of radiation by an unstable atomic nucleus beta particle alpha particle radioactive decay 7/10 radioactive isotopes that can be followed through the steps of a chemical reaction or a industrial process. tracer radio activity alpha particle 8/10 a class of elements characterized by physical properties that include shininess, malleability, ductility, and conductivity reactivity metal alki metal 9/10 the ability of an abject to transfer hear or electricity to another object malleable corrosion conductivity 10/10 the elements in group 18 of the periodic table noble gasses tracer ductile