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Valence Electrons and Chemical Families

Aug 20, 2022

Key Concepts

  • Atom
  • Shell
  • Valence Electrons
  • Stability


Atoms are the basic unit of every object around us. There are three subatomic particles in an atom. They are: electrons, protons and neutrons. Protons and neutrons together are called the nucleus. Electrons revolve around the nucleus in the path called the shells or orbits. 


Each orbit or shell of an atom has its own capacity. The outermost orbit is the farthest orbit from the nucleus. It is called the valency orbit or valence shell, and the electrons present in it are called the valency electrons.  



As discussed earlier, the capacity to hold electronsdiffer for each orbit. The first orbit of an atom can contain a maximum of 2 electrons. The second and third shell of an atom can hold a maximum of 8  and 18 electrons, respectively, and the fourth shell can hold a maximum of 32 electrons.  

electron shell diagram

The distance of the orbits increases as the number of orbits increases. The value of the number of shells is denoted by n. It is always a natural number.  

When the distance of the valency orbit increases from the protons in the nucleus, the removal or the addition of the electron to the valency orbit becomes easier as compared to the electrons present in the inner orbits.  


We already know the elements are arranged in a tabular form called the periodic table. The groups of the periodic table are the rows and the periods are the columns of the table. The count of the valence electrons in each group is fixed. For example, the alkali group metals present in the first row of the periodic table have one valence electron, i.e., it contains 1 electron in its outermost shell.  

periodic table

The alkaline metals, the second group of the table, contains two valence electrons, i.e., the outermost orbit of this atom contains two electrons.  

The period number represents the number of shells in an atom. The group number defines the valence electrons present in the element. 

Noble gas stability: 

If every orbit in the atom is completely filled with its maximum number of electrons that it can hold then such atoms are the most stable elements. These are named as the Noble Gas family or the inert gas. These are at the rightmost column of the periodic table. As all the orbits of an atom are filled, the new electrons, if added, need a new orbit. This makes the atom unstable. The main reason for the stability of the noble gas elements is the completely filled orbits of the atom.  

Each and every element in the periodic table wants to attain the stability of  noble gas as they are the most stable element in the periodic table. Stability is attained either by losing or gaining or sharing of electrons. 



  • Atoms are the basic unit of every element.
  • The electrons are arranged around the nucleus in different paths called the orbit.
  • The outermost orbit is called the valence shell and the electrons in that orbit are called valence electrons.
  • The elements in the same group of the periodic table share the same electronic configuration.
  • The elements in the same group share the other physical and chemical properties like ductile nature, conductivity, and reactivity.
  • Since the valence shell in the noble gas is filled with electrons, they are the stable elements in the periodic table.


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