Question

How do you determine the valence electrons?

Answer 1

As we know that the atomic number of the atom represents the number of electrons present in the atom. The electrons are represented in the electronic configuration where the valence electrons are present in the outermost orbital.

Complete step by step answer: The atom contains three subatomic particles: protons, neutrons, and electrons. The nucleus of the atom present at the center of the atoms contains the positive charge protons and the neutrons are the neutral charge species. The negatively charged electrons are surrounding the atom in a circular orbit.
The electrons present in the atom or chemical element is represented by the electronic configuration of the atom. The number of electrons present will be filled in the orbitals of the atom which represents the atomic number of the atom. The number of electrons as well as the atomic number increases as we move in the periodic table.
First we should know what valence electrons are. The valence electrons are defined as those electrons which are present in the outermost orbital of the electronic configuration.
Example: Let’s take the chemical element beryllium. The atomic number of beryllium is 4. It is an s-block element present in Group 2. The total number of electrons present in the beryllium atom is 4. The electronic configuration of beryllium is $1{s^2}2{s^2}$ where two electrons are present in 1s-orbital and two electrons are present in 2s-orbital. The $1{s^2}$ is the electronic configuration of helium so the electronic configuration of beryllium can also be given as $[He]2{s^2}$. The valence electrons present in the outermost orbit is two.

Note:
The valency of the chemical element is determined by the number of valence electrons present in the outermost electronic configuration. The elements present in the same group have the same number of valence electrons.