関連ワード:  give examples of covalent compounds    two examples of covalent compounds    3 examples of covalent compounds    some examples of covalent compounds    two examples of covalent compounds found in the environment    give examples of covalent bond    give two examples of covalent compounds    give 5 examples of covalent compounds    give 10 examples of covalent compounds    5 examples of covalent compounds and their uses