1. Sodium loses 1 electron when making a chemical bond.
2. Phosphorus gains 3 electrons when making a chemical bond.
3. Iron and copper; they form multiple ions with different charges (e.g., Fe²⁺, Fe³⁺ and Cu⁺, Cu²⁺).
4. Bromine, chlorine, fluorine, iodine.
5. One atom of calcium; calcium has a +2 charge and oxide has a -2 charge, so they combine in a 1:1 ratio to balance charge.
6. Three sodium ions; nitride has a -3 charge and each sodium ion has a +1 charge, so three sodium ions are needed to balance the charge.
7. Two potassium atoms and one sulfur atom; potassium has a +1 charge and sulfide has a -2 charge, so two potassium ions are needed to balance one sulfide ion.
Parent Tip: Review the logic above to help your child master the concept of positive and negative ions worksheet answer key.