An electrically neutral group of two or more atoms held together by covalent chemical bonds *

That property of an object that resists acceleration and couples to gravity, thereby giving it weight *

Particle with a negative elementary electric charge *

A unit of energy or work equal to the energy expended (or work done) in applying a force of one newton through a distance of one meter *

A particle consisting of two protons and two neutrons bound together into a particle identical to a helium nucleus *

Variants of a particular chemical element that share the same number of protons, but differ in number of neutrons *

Equal to 1.602176565(35)×10−19 J *

Acts gravitationally but doesn't couple to light *

Chemical elements that are radioactive and release energy upon radioactive decay *