Question

Describe how hydrogen and oxygen form water.

Answer 1

Hydrogen and Oxygen by themselves have 1 and 6 valence electrons, respectively. 8 valence electrons is stable, so the atoms form bonds with each other to achieve 8 valence e-.

1 H atom + 1 H atom + 1 O atom = 8 valence e-

Answer 2

The oxygen atom requires 2 electrons to complete its valance shell. Hydrogen is special in that it can eighter give or take one electron and still be stable. So hydrogen gives its electron  to oxygen, and two hydrogens fill up all of oxygen's  valance shell, and it forms water.