Sau đây là đáp án của câu 6:
(1) Covalent bonds, in which an electron pair is shared between the two atoms A: B, and
(2) Ionic bonds, formed by transfer of one or more e^ns to form a positive cation and negative anion, i.e., A+: B-, Metallic (left side of the periodic table) elements usually form ionic bonds with nonmetallic (H and those on the right side the periodic table) elements. Nonmetallic elements form covalent bonds each other and to themselves. All organic compounds have covalent bonds ...…some also have ionic bonds