Chapter 2.7, Problem 2.17P

Interpretation Introduction

Interpretation:

Incomplete filled sub shell and number of paired or unpaired electrons of the element should be identified.

Concept introduction:

The periodic table is given below,

Electronic configuration:

The electron configuration is the distribution of electrons of an atom or molecule in atomic or molecular orbitals.

1. (1) Electrons start occupying from the lowest energy orbitals. The increasing order of orbital energy is $\text{s, p, d and f}$. The lowest energy orbital is $\text{1s}$. The order of energy of the orbital for the first three period is given below,

   $\text{1s, 2s, 2p, 3s,}\text{and 3p}$.

2. (2) The orbital which is closer to the nucleus has lower energy; therefore the 2s is lower in energy than 3s. Accordingly $2s$ is lower in energy than $\text{2p and 4s}$ is lower in energy than $\text{3d}$.
3. (3) In general, the orbitals can hold maximum of two electrons, the two electrons must have opposite spin.

The subshell ordering by Aufbau’s principle is given below, $\text{1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, 8s, }\mathrm{...}$