Pure water has a pH of 7.0. However, normal rain is slightly acidic because carbon dioxide (CO2) dissolves into it forming weak acid, giving the resulting mixture a pH of approximately 5.6 at typical atmospheric concentrations of CO2.

Carbonic

Explanation:

Rain water is slightly acidic with a pH of 5.6. This happens due to the rain water reacting to atmospheric Carbon dioxide in atmospheric concentrations.

H20+ CO2= H2CO3 (carbonic acid)

The Hydrogen ions in the H2CO3 ( weak Carbonic acid) makes the water acidic. This explains the reason why rain water is referred to as acidic water.

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.