Balancing chemical reactions

[406025813]

My question about atomic balances, I understand how to make them but when making the balance I get confused when we join it to the water or to another element how do we know which element will go?

[405972194]

Usually elements are combined due to opposite charges (i.e. positive atoms will connect with negative atom). If there is ever an ion that is unchanged on both sides of the chemical equation (spectator ion) it will be dropped.