Question

The electronic states $X$ and $Y$ of an atom are depicted below:
$X:1s^{2}2s^{2}2p^{6}3s^1$
$Y:1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^1$
Which of the following statements is not correct?

• A. X represents an alkali metal.
• B. Energy is required to change X into Y.
• C. Y represents ground state o f the element.
• D. Less energy is required to remove an electron from X than from Y.

Answer 1

Answer: (D)

Electronic configuration for given elements $X=1s^{2}2s^{2}2p^{6}3s^1,Y=1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^1$ shows that they belong to the same group (group 11, alkali metals) and $Y$ is bigger in size than X. Thus, the distance between the nucleus and valence shell in Y is greater as compared to $X$ and therefore $Y$ experience less effective nuclear charge and needs less energy to remove the valence electron than that from $X$ atom.