The most important two points to remember are:
- The Period (or Row #) = The Atom's # of Electron Shells
(Rows are horizontal, left-to-right. Remember: You have 7 periods during the day, and there are 7 periods, or rows, on the Periodic Table.)
- The Groups (or Column #) = The Atom's # of Valence Electrons
(Columns are vertical, up-and-down. Valence Electrons are the electrons on the outer-most shell, called the "valence" shell.)