Question

Match the column I with column II and mark the appropriate choice.

	Column I (Atom)		Column II (No. of unpaired electrons)
(A)	${}_{15}P$	(i)	6 unpaired electrons
(B)	${}_{24}Cr$	(ii)	2 unpaired electrons
(C)	${}_{26}Fe$	(iii)	3 unpaired electrons
(D)	${}_{14}Si$	(iv)	4 unpaired electrons

• A. $\left(A\right)\to \left(ii\right),\left(B\right)\to \left(i\right),\left(C\right)\to \left(iii\right),\left(D\right)\to \left(iv\right)$
• B. $\left(A\right)\to \left(i\right),\left(B\right)\to \left(iii\right),\left(C\right)\to \left(ii\right),\left(D\right)\to \left(iv\right)$
• C. $\left(A\right)\to \left(iii\right),\left(B\right)\to \left(i\right),\left(C\right)\to \left(iv\right),\left(D\right)\to \left(ii\right)$
• D. $\left(A\right)\to \left(iv\right),\left(B\right)\to \left(ii\right),\left(C\right)\to \left(i\right),\left(D\right)\to \left(iii\right)$

Answer 1

Answer: (C)

$\left(A\right)\to \left(iii\right),\left(B\right)\to \left(i\right),\left(C\right)\to \left(iv\right),\left(D\right)\to \left(ii\right)$

A. ${}_{15}P=1s^{2}2s^{2}2p^{6}3s^{2}3p^3$

Valence shell configuration is: $3s^{2}3(p_x^1,p_y^1,p_z^1)$

Number of unpaired electron=3 in 3p-orbital=(iii)

B. ${}_{24}Cr=1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{5}4s^1$

Valence shell configuration is: $4s^{1}3(d_{z^2}^1,d_{x^2-y^2}^1,d_{xy}^1,d_{yz}^1,d_{zx}^1)$

Number of unpaired electron=6 in 4s and 3d-orbital=(i)

C. ${}_{26}Fe=1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{6}4s^2$

Valence shell configuration is: $4s^{2}3(d_{z^2}^2,d_{x^2-y^2}^1,d_{xy}^1,d_{yz}^1,d_{zx}^1)$

Number of unpaired electron=4 in 3d-orbital=(iv)

D. ${}_{14}Si=1s^{2}2s^{2}2p^{6}3s^{2}3p^2$

Valence shell configuration is: $3s^{2}3(p_x^1,p_y^1,p_z^0)$

Number of unpaired electron=2 in 3p-orbital=(ii)

thus A-(iii),B-(i),C-(iv),D-(ii)