Which statement best describes the properties of covalent compounds?

A.
They are always solid at room temperature, are brittle, and have a high melting point.
B.
They may be gases, liquids, or solids at room temperature, and have a low melting and boiling point.
C.
They are always composed of an equal proportion of cations to anions.
D.
They are always liquid at room temperature, and have a high melting and boiling point.
E.
They are good conductors of heat and electricity, and are ductile and malleable.

B

Explanation:

If something says always, you have to know for sure that it's true otherwise don't pick it. Covalent compounds have non-metals like carbon(s), oxygen(g), and bromine (l)

 B. They are always liquid at room temperature, and have a high melting and boiling point.

Explanation: A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding. Hence the bonding is relatively weak thus have low melting and boiling point. On the other hand, ionic compounds are formed by the transferring of electrons thus strong electrostatic forces are present and require a large amount of energy to break it apart hence boiling and melting points are high.

For example

The molecule carbon tetrachloride is a non-polar covalent molecule, CCl4. Its melting point is -23°C. By contrast, the ionic solid NaCl has a melting point of 800°C.

Properties  of Covalent Compounds

1. Gases, liquids, or solids (made of molecules)  

2. Low melting and boiling points  

3. Poor electrical conductors in all phases  

4. Many soluble in nonpolar liquids but not in water

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c- cold periods in earth's history during which glaciers covered much of the surface.

explanation: