Which phrase would be incorrect to use (a) A molecular of a compound (b) A molecule of an element (c) An atom of an element (d) None of these
An atom of a compound is the INCORRECT usage. Since molecules are the building blocks of a compound, therefore the correct usage would be "A molecule of a compound". A compound has molecules made of atoms of different elements. Since an element is formed from atoms, "An atom of an element" is correct to use.
