The mass of a $${}_3^7Li$$ Li nucleus is 0.042 u less than the sum of the masses of all its nucleons. The binding energy per nucleon of $${}_3^7Li$$ nucleus is nearly

The energy of a hydrogen atom in the ground state is $$-$$ 13.6 eV. The energy of a He⁺ ion in the first excited state will be

An alpha nucleus of energy $${1 \over 2}$$ mv² bombards a heavy nuclear target of charge Ze. Then the distance of closest approach for the alpha nucleus will be proportional to

The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an