ANSWER
3. both covalent and ionic
EXPLANATION
Sodium Phosphate is an ionic compound formed by two ions, Sodium Na+ and Phosphate PO−3 . In order for these two polyatomic ions to bond the charges must be equal and opposite. Therefore, it will take three +1 sodium ions to balance the one -3 phosphate ion. However, polyatomic ions are held together by covalent bonds, so this compound contains both ionic and covalent bonds.
