A proton having mass equal to $$1.66 \times 10^{-27} \mathrm{~kg}$$ is accelerated to one tenth of the velocity of light. If its velocity can be measured to an accuracy of $$\pm 2 \%$$, what would be the uncertainty in its position?

The energy of an electron in the ground state of Hydrogen atom is $$-2.18 \times 10^{-18} \mathrm{~J}$$. What would be the energy associated with the second excited state of $$\mathrm{Li}$$ ?

Minimum number of nodes are present in

$$\mathrm{O^{2-},F^-,Mg^{2+},Al^{3+},O_2,F_2}$$. How many of the species given above isoelectronic?