Question

Write the electronic configuration of each one of Li (3), Na (11) and K (19) and answer the following question:

What is the valence shell of element K?

Answer 1

Step-1: Introduction

The elements in periodic table are placed in periods and groups. Periods are horizontal rows that has increasing atomic numbers. Groups are vertical columns. There are 7 periods and 18 groups in periodic table.

Step-2: Electronic configuration

Atomic numbers of Lithium ($\mathrm{Li}$), Sodium ($\mathrm{Na}$) and Potassium ($\mathrm{K}$) are 3, 11 and 19 respectively.

Electronic configuration of Lithium = (2, 1).

Electronic configuration of Sodium = (2, 8, 1).

Electronic configuration of Potassium = (2, 8, 8, 1).

Step-3: Valence shell

The valence shell is the shell where valence electrons of the element are present.

Potassium has 2 electrons in K-shell, 8 electrons in L-shell, 8 electrons in M-shell and 1 electron in N-shell. So, the number of valence shell is 4.

Therefore, the valence shell of Potassium is N-shell.