Answer:
See explanation
Step-by-step explanation:
Hydrogen has a valency of +1 or -1. Its electronic configuration is 1s1.
The 1s sub-level (first shell) is known to hold two electrons. This means that hydrogen may either loose this one electron in the 1s level to yield H^+ or accept another electron into this 1s level to form H^- (the hydride ion).
The formation of the hydride ion completes the 1s orbital.