Question

The valency of an element is:
A.The mass of the element displaying 1part by the mass of hydrogen
B.The mass of the element combining with 8 parts by mass of oxygen
C.The number of atoms of hydrogen combining with 1 atom of the given element
D.The number of atoms in 1 molecule of the given element.

Answer 1

Hint: We can say valency is the combining power of an element. Elements that belong to the same group of the periodic table contain the same valency. The valency of an element is based on the number of electrons present in the outer shell.

Complete answer:
We can say that the number of hydrogen atoms, which could combine with or replace one atom of the element either directly or indirectly is the valency of an element.
In other words, we can say that the valency of an element is the number of electrons an atom of the element used to combine with atoms of other elements. It is the combining power of an atom of the element. In an atom, the outermost electrons are the electrons, which could be used in combining with other atoms. These are the electrons in the orbitals of the outermost shell known as the valence shell and the electrons are called valence electrons.
$\therefore $ Option (C) is correct.

Note:
We have to know that the elements of noble gases (or) group-18 elements show zero valency as they do not combine with other elements due to their completely filled orbitals.
-The elements that belong to group-1 have a valency of one $\left( { + 1} \right)$.
-The elements that belong to group-2 have a valency of two $\left( { + 2} \right)$.
-The elements that belong to group-13 have a valency of three $\left( { + 3} \right)$.
-The elements that belong to group-14 have a valency of four $\left( { + 4/ - 4} \right)$.
-The elements that belong to group-15 have a valency of three $\left( { - 3} \right)$.
-The elements that belong to group-16 have a valency of two $\left( { - 2} \right)$.
-The elements that belong to group-17 have a valency of one $\left( { - 1} \right)$.