Question

How many valence electrons are in an atom of chlorine?

Answer 1

Hint The electrons which are present or located in the outermost orbit of an element or atom are called valence electrons. To know about the valence electrons present in an atom we should know the atomic number of the element.

Complete step by step answer:
- In the question it is asked to calculate the valence electrons present in the chlorine atom.
- The atomic number of chlorine is 17 and it is present in group 17 and belongs to p-block in the periodic table.
- Chlorine belongs to the group of halogens.
- Means chlorine contains 17 electrons in its electronic configuration.
- The electronic configuration of the chlorine is $1{{S}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{5}}$ .
- The electrons in $3{{s}^{2}}3{{p}^{5}}$ are called outermost electrons and they are not completely filled.
- Means chlorine has 7 valence electrons which are present in 3s and 3p orbitals.
- At the time of the chemical reaction with other atoms the valence electrons are going to play a big role.
- Few compounds will lose the valence electrons to get stability and few atoms accept electrons to make the valence electrons to get the octet configuration to get more stability.
- The acceptance of electrons is going to depend on the electronegativity of the atom.

- Therefore the number of valence electrons in chlorine is 7.

Note: Chlorine is the halogen and the halogens have highest electronegativity values when compared to remaining elements in the periodic table. We should know the atomic number of the element to know about the valence electrons present in it.