Questions

An owl.

"What noise does an owl make?

The sound an Owl makes, it sounds like, "Who?" to our ears.

They sounds entire lives asking the same question, but they'll never give any answers.

When atoms react they do so in order to reach the lowest energy, which is the most stable. The electrons orbitals will overlap in the way that reduces the energy the most. Orbitals of similar energy will produce the greatest stabilisation.The answer you gave isn't the whole story, it depends what species is reacting with what. The effective nuclear charge on the atom will affect the energy of the valance electrons.

Hence, the reactivity of an atom arises from the existence of unpaired electrons in the valence shell.

Colored aqueous solutions are a characteristic of transition compounds.

The only transition compound in the above choices is CrCl3.

Cr is a transition element.