Valency meaning in chemistry

The electrons present in the outermost shell of an atom are called Valence electrons.

From the Bohr-Bury scheme, we find the outermost shell of an atom can accommodate a maximum of 8 electrons.

Also, the atoms of the elements show little chemical activity if its outermost shell is completely filled. Also can be said that the elements combining capacity or its valency is zero.

In the inert elements, the helium atoms have two electrons in their outermost shell and all other elements have atoms with 8 electrons in the outermost shell.

The combining capacity of atoms of other elements to react or form molecules with atoms of the same or different elements were the attempts to attain a fully filled outmost shell.

An outermost shell that has 8 electrons is said to be octet.

The atoms would attempt or react to achieve an octet in the outermost shell and this process will be done by gaining, losing, or sharing the electrons.

The losing, gaining, or sharing of electrons gives the direct combining capacity of the elements.

Example Sodium/lithium/hydrogen atoms contain one electron each in its outermost shell so as to lose one electron. These elements are said to have a valency of One (1).

Similarly, the valency of Magnesium is 2, as it has 2 electrons in the outermost shell and aluminum is 3 as it has 3 electrons in the outermost shell.

Valency of Metals

Metals have positive valency as they have +1,+2,+3 electrons in their outermost or valance shell.

The metal having valency ‘1’ is potassium its chemical symbol is K . Potassium is an alkali metal and belongs to Group 1 of the periodic table.


Combining capacity Meaning

It is the ability to make bonds with other elements. The number of valence electrons of an atoms given the combining capacity.

Metal having valency 1

Alkali metals has one valency electrons. These belongs to first group of periodic table. Ex: Hydrogen.

The electrons present in the outermost shell are called ?

The electrons present in the outermost shell are called valence electrons and the outermost shell is called valence shell.

* * All the Notes in this blog, are referred from Tamil Nadu State Board Books and Samacheer Kalvi Books. Kindly check with the original Tamil Nadu state board books and Ncert Books.