Groups on the Periodic Table

Hydrogen is a special element because it is not like any other group of elements. It is placed above Group 1 in the periodic table because it has one electron in its valence shell but does not belong in the alkali metals group. Hydrogen is found in stars and it is the most abundant element in the universe. However, it only makes up one percent of the Earths mass. On Earth, most hydrogen is combined with oxygen in the form of water.