Why a nucleus has mass less than the sum of the masses of the individual nucleons in it.

Why I_1 of Al is less than that of Mg?

Is the sum of two natural numbers always more than the individual numbers.

Why is the density of the nucleus more than that of the atom ? Show that the density of nuclear matter is same for all nuclei.

What are abnormal molar masses? Why are the molar masses abnormal ?

Statement 1: In an ellipse the sum of the distances between foci is always less than the sum of focal distances of any point on it. Statement 2: The eccentricity of any ellipse is less than I.