Chapter 2.8, Problem 2.20P

Interpretation Introduction

Interpretation:

The group should be identified for the elements that has valance electronic configuration as ${\text{ns}}^{\text{2}}$.

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 occupy in 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 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 principle is given below, $\text{1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, 8s, }\mathrm{...}$

s-Block element:

It is called as main group elements that result from the filling of an s orbital.

p-Block element:

It is also called as main group elements that result from the filling of an p orbital.

d-Block element:

It is called as transition metal elements that result from the filling of an p orbital.

f-Block element:

It is called as inner transition metal element that results from the filling of an p orbital.