Give the chemical symbol of an element in the third period (row) of the periodic table with three valence electrons. express your answer as a chemical symbol

Aluminium or Al has 13 electrons. 2 fall into the first energy level and 8 fall into the second energy level which means there are 3 more electrons in the outermost energy level, meaning you have 3 valence electrons.

The molecules contain like 54 of water 

16- counting by fours