Hydrogen Is Unique Among the Elements Because ________

Hydrogen is unique among the elements because ________. 1. It has only one valence electron.
2. It is the only element that can emit an atomic spectrum.
3. Its electron is not at all shielded from its nucleus.
4. It is the lightest element.
5. It is the only element to exist at room temperature as a diatomic gas.

A) 1, 2, 3, 4, 5
B) 1, 3, 4
C) 1, 2, 3, 4
D) 2, 3, 4
E) 3, 4