1/10/2012 What does the period (row) on the periodic table tell you about elements in that row?

The groups show elements with a similar valence structure. The elements on the very left, for example, have 1 valence electron. This electron configuration tends to make them very reactive. The groups towards the right tend to have more valence electrons, but the orbitals are slowly filling up, meaning the elements at the right have stable orbitals.