Final answer:
Compound d) CH2O is formed by a covalent bond; it consists of nonmetals carbon, hydrogen, and oxygen. In comparison, other compounds listed (NaCl, CaCl2, NaBr) include metals and nonmetals, indicating ionic bonds.
Step-by-step explanation:
To determine which compounds are formed by a covalent bond, we should consider the elements involved in each compound. Compounds a) NaCl, b) CaCl2, and c) NaBr consist of a metal (sodium or calcium) and a nonmetal (chlorine or bromine), indicating that they are ionic compounds. They form through the transfer of electrons from the metal to the nonmetal. On the other hand, d) CH2O consists of carbon, hydrogen, and oxygen, which are all nonmetals, and typically nonmetals form covalent bonds by sharing electrons. Therefore, d) CH2O is the compound formed by a covalent bond.
Now let's address the Check Your Learning section:
- (a) SO2: Sulfur and oxygen are nonmetals, thus SO2 is covalent.
- (b) CaF2: Calcium is a metal and fluorine a nonmetal, so CaF2 is ionic.
- (c) N₂H4: Nitrogen and hydrogen are nonmetals, so N₂H4 is covalent.
- (d) Al2(SO4)3: Aluminum is a metal and sulfate is a polyatomic ion, making Al2(SO4)3 ionic.