Structure Of Atom Ques 55
55. The order of filling of electrons in the orbitals of an atom will be
[1991]
(a) $3 d, 4 s, 4 p, 4 d, 5 s$
(b) $4 s, 3 d, 4 p, 5 s, 4 d$
(c) $5 s, 4 p, 3 d, 4 d, 5 s$
(d) $3 d, 4 p, 4 s, 4 d, 5 s$
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Solution:
- (b) The sub-shell with lowest value of $(n+l)$ is filled up first. When two or more sub-shells have same $(n+l)$ value the subshell with lowest value of ’ $n$ ’ is filled up first therefore the correct order is orbital $\quad 4 s \quad 3 d \quad 4 p \quad 5 s \quad 4 d$ $n+l \quad 4+0 \quad 3+2 \quad 4+1 \quad 5+0 \quad 4+2$ $\begin{matrix} \text{ value } & =4 & 5 & 5 & 5 & 6\end{matrix} $
BETA
