Answer:
1) NaCl, 5)MgS
Explanation:
What makes something an Ionic Bond:
For 1) Na has a charge of 1+ and Cl has a charge of 1-. They both come together to form table salt. Their electronegativity is also larger than 2.0. Also Na is a metal and Cl ion is a nonmetal.
For 2) C and O are both nonmetals and are covalent bonds
For 3) Water is a polar covalent molecule because there is a electronegativity difference between H and O, but not great. H and O are also nonmetals.
For 4) While Fe is a metal and O is a nonmetal, their electronegativity difference is not greater than 2.0. This makes it polar covalent.
For 5) Mg is a metal and S is a nonmetal. They have a large electronegativity difference. Also Mg has a charge of 2+ while S has a charge of 2-.