The melting points of the oxides of the third-period elements are given in parentheses:

A) Ionic, B) Ionic, C) Ionic, D) Covalent, E) Molecular, F) Covalent, G) Covalent

Explanation:

The ionic crystals are formed when a metal loses electrons, forming a cation, and a nonmetal gains those electrons, forming an anion. The covalent crystals are those in that two nonmetals share pairs of electrons, and when they are large, it's called a molecular crystal. The metallic crystals are those formed by metals only.

A) Na is metal and O is a nonmetal, so it's ionic.

B) Mg is metal and O is a nonmetal, so it's ionic.

C) Al is metal and O is a nonmetal, so it's ionic.

D) Both Si and O are nonmetals, so it's covalent.

E) Both P and O are nonmetals, but the crystal has a large number of atoms, so it's molecular.

F) Both S and O are nonmetals, so it's covalent.

G) Both Cl and O are nonmetals, so it's covalent.

lithosphere

Explanation:

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