H2 is a covalent bond. Each hydrogen atom shares its single electron to the other, so each hydrogen has two valence electrons (full outer shell).
The number is 25. The square root of 25 is 5 and 5x2 is 10 and then 10+5 is 15
5. Eubacteria
6. Plantae
7. Animalia
8. Protist (technically not a kingdom)
9. Archaebacteria
10. Fungi