Answer
Explanation:
Sodium is a group 1 element which means it has 1 electron in its outer shell
Chlorine is a group 7 element which means it has 7 electrons in its outer shell
All atoms need 8 electrons in their outer shells to be happy so when Sodium and Chlorine react, Sodium loses the electron in its outermost shell, and Chlorine receives it. So Chlorine's outermost shell is saturated as it now has 8 electrons and Sodium now has its middle shell as it's outermost shell (so it now has 8 electrons in its outermost shell).
So since sodium lost an electron it now has a positive charge of 1+ and Chlorine has a negative charge of 1- because it gained an electron (Protons have a positive charge, Neutrons have no charge and Electrons have a negative charge). So since Sodium has a positive charge and Chlorine has a negative charge they attract each other and form what is called an ionic bond (a bond that is formed between ions of opposite charge) because of this ionic bond the Sodium and Chlorine atoms stick together and form Sodium Chloride (which is table salt)
