Column A
horizontal rows on the periodic table
periods
the number of protons in the nucleus of an atom
atomic number
an electron in the outermost energy level of an atom
valence electron
vertical columns also known as families
groups
the subatomic particle that is electrically neutral and found in the nucleus of an atom
neutron
particles found in the nucleus of an atom
protons and neutrons
subatomic particles orbiting around the nucleus
electrons
the pair of particles that balance the charge of an atom
protons and electrons