How could you determine in a lab if a certain color is a chemical property of a substance, or if the color is caused by other factors?

There are  3 types of chemical bonds:

1) Ionic: A bond formed by the transfer of electrons from from one atom to the other

2) Covalent : A bond formed by sharing of electrons between atoms

3) Metallic: A bond formed by the electrostatic attraction between metal ions and delocalised electrons.

Metals are electropositive, i.e. they have a tendency to lose electron. In a metallic lattice, this creates positively charged ions surrounded by negatively charged electrons which are held  by electrostatic forces of attraction.

Ans: E) They form because electrons move freely between atoms.