Question

Silicon atomic number 14 and phosphorus atomic number 15 belong to the same period of the periodic table. Write down the electronic configuration of silicon and phosphorus and name the period in which these elements occur.

Answer 1

Modern periodic table:

• The modern periodic table is an arrangement of all the elements known in accordance with their increasing atomic number and recurring chemical properties.
• It is a tabular display of 118 chemical elements which consists of horizontal rows called periods and vertical columns are called groups.
• All elements in a group have the same number of valance electrons, and in period elements have the same number of electron shells.

Electron configuration:

• Electronic configuration, also called electronic structure, is the arrangement of electrons in energy levels around an atomic nucleus.
• The electron configuration of an element describes how electrons are distributed in its atomic orbitals.
• It can be written in K, L, M, and N format. Where the K, L, M, and N shells represent the energy shells.
• The total number of an electron in the shell is given by the formula$\text{2}{\text{n}}^{\text{2}}$, where n is the shell number.
• For the K shell maximum number of electrons that can be acquired is 2.
• For the L shell maximum number of electrons that can be acquired is 8.
• For the M shell maximum number of electrons that can be acquired is 18 and so on.

The electronic configuration for Silicon having atomic number 14 is 2,8,4.

The electronic configuration for Phosphorus having atomic number 15 is 2,8,5.

So it is clear from the electronic configuration that both these elements have 3 shells each therefore they belong to period number 3.