Question

How do you determine the number of valence electrons?

Answer 1

Electron is the subatomic particle that is negatively charged and present around the nucleus of an atom in the shells. The outermost shell of an atom is known as the valence shell and the electrons present in it are called valence electrons. Valence electrons are very important which decides the oxidation number of an element also the numbers of the bonds formed by an atom in the compound.

Complete step by step answer:
- As we know that valence electrons are nothing but the electrons present in the valence shell of an atom or species.
- To determine the valence electrons it is important to know the periodic table. As we know that the periodic table consists of eighteen columns and seven rows. The vertical columns are called groups and the horizontal rows are called periods.
- There are four blocks in the periodic table s-block, p-block, d-block, and f-block. In the case of the s and p block elements, the group number is nothing but the numbers of the valence electrons.
For example: 1. In the case of the lithium, sodium, potassium elements the numbers of the valence electrons are one. As these are s-block elements and included in the first group of the periodic table.
2. Another example is oxygen which is a p-block element included in group 16(6A) and possesses 6 valence electrons.
- In this way in the case of the s and p block elements group number indicates the numbers of the valence electrons.
- In the case of the d and f block elements, the electronic configuration of the atom gives the idea about the numbers of the valence electrons present in the atom.
For example scandium, it is a d- block element having electronic configuration is $\left[ {{\text{Ar}}} \right]{\text{3d}}{\,^{\text{1}}}{\text{4}}{{\text{s}}^{\text{2}}}$. Here, 4s is the valence shell and the electrons present in it are 2. Hence, the valence electrons in the scandium are two.
- In this way by using the group number and the electronic configuration of the atom we can determine the number of the valence electrons in it.

Note: As we know that valence electrons are nothing but the electrons present in the valence shell of an atom or species. To determine the valence electrons it is important to know the periodic table. As we know that the periodic table consists of eighteen groups and seven periods. In the periodic table s-block, p-block, d-block, and f-block are the four blocks in which all known elements are placed. The position of an element in the periodic table is important in determining the number of valence electrons.