## Algebra 1

Since there are 18 electrons which have a charge of -1, the total negative charge is $18(-1)$. Since there are 16 protons which have a charge of +1, the total positive charge is $16(1)$. Add the positive and negative charges to find the ion's charge. $18(-1)+16(1)\longrightarrow$ multiply $=-18+16\longrightarrow$ add $=-2$