An oxygen atom has eight protons and a hydrogen atom has one proton, How many electrons are in a hydroxide ion?
A. 8
B.9
C.10
D. none

The answer is C.

Explanation:

When hydrogen react with oxygen to form hydroxide ion, the electron in each element will add up together.

So 8-electrons of oxygen react with 1-electron of hygrogen to form 10-electrons of hydroxide.

In an element, atomic number(proton number) is equal to numbet of electrons.

answer; the above statement is (true);

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.