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 $X=1 s^{2} 2 s^{2} 2 p^{6} 3 s^{1}, Y=1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{1}$ 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.