Question

How many valence electrons does phosphorus have?

Answer 1

Hint: Electrons which are present in the outermost shell of the atom are known as valence electrons and for the calculation of the number of valence shell electrons we should know about the electronic configuration of the atom.

Complete Solution :
Symbolically Phosphorous is denoted as ‘${\text{P}}$’ in the periodic table and its atomic number is 15.
-As we know that the atomic number $\left( {\text{Z}} \right)$ of an atom is always equal to the number of protons present inside the nucleus or number of electrons present in the orbitals outside the nucleus.
i.e. Atomic Number = No. of protons = No. of electrons
-So, the number of electrons in the Phosphorus atom is 15 because it is present in the neutral state.
-Electronic configuration of Phosphorus is shown as follow:
$1{s^2},2{s^2}2{p^6},3{s^2}3{p^3}$
Hence, from the above given configuration it is clear that the number of valence electrons in the Phosphorus atom is five.

Additional information-
 Phosphorus is present in the VA group of the periodic table and it is a non – metal. Chemically it is reactive in nature that’s why it is not present in a free state. Its appearance is white and red because it is present in two forms as white phosphorus and red phosphorus respectively in nature.

Note: Here some of you may do wrong calculation if you only count p-orbital electrons and leave s-orbital electrons. During the calculation of valence electrons always add electrons present in the s-orbital as well as in p-orbital of the outermost shell.