A ion that gains electrons is called what

anion

Explanation:

Atoms consist of electrons, protons and neutrons. ... When an atom gains or loses an electron, it attains a net charge and becomes an ion. When electrons are lost (or donated), the resulting ion is called cation. When electrons are gained, the resulting ion is called an anion.

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.