Sharing electrons: A hydrogen example

Hydrogen is number 1 on the periodic table  upper-left corner. Hydrogen has one valence electron. It’d love to gain another electron to fill its 1s energy level, which would make it isoelectronic with helium (because the two would have the same electronic configuration), the nearest noble gas. Energy level 1 can hold only two electrons in the 1s orbital, so gaining another electron would fill it. That’s the driving force of hydrogen: filling the valence energy level and achieving the same electron arrangement as the nearest noble gas.