Answer
-2
Work Step by Step
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
$=-2$
