Chapter 2, Problem 2.50AP

Interpretation Introduction

Interpretation:

The reason should be explained for the third period in the periodic table contains eight elements.

Concept introduction:

The Aufbau principle:

The aufbau principle is states that in the ground state of an atom, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. For example, the 1s shell is filled before the 2s subshell is occupied.

The subshell ordering by this rule is

$\text{1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, 8s, }\mathrm{...}$

Number of electrons in the shells is given below,

Each shell contains only a fixed number of electrons. The first shell contains two electrons, the second shell contains eight (2 + 6) electrons, the third shell contains 18 (2 + 6 + 10), fourth shell contains (2 + 6 + 10 + 14 ) and so on.