Question

compare the radii of two species X and Y . give reasons for your answer
A) X has 12 protons and 12 electrons
B) Y has 12 protons and 10 electrons

Answer 1

If the number of proton is same then species with lower number of electrons will be smaller in size because of stronger pull of proton.
Y will have the smaller radius than X because the number of proton is more than electrons. As the number of proton is more , it will pull the electrons more strongly than X that results in smaller size of Y than X.