Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Valency is defined as the combining capacity of an atom of an element. It determines how atoms of one element will react with atoms of another element.
The electrons present in the outermost shell of an atom are called valence electrons. These electrons take part in chemical reactions.
According to the Bohr-Bury scheme, the outermost shell of an atom can accommodate a maximum of electrons (except for the shell, which can hold ).
The Octet Rule states that atoms react to achieve a completely filled outermost shell (eight electrons), which represents a stable electronic configuration.
If the number of valence electrons () is or , the valency is generally equal to . For atoms with or valence electrons, the valency is calculated as .
Noble gases like Helium (), Neon (), and Argon () have completely filled outermost shells. Therefore, their valency is as they are chemically inert.
📐Formulae
💡Examples
Problem 1:
Calculate the valency of Magnesium () given its atomic number is .
Solution:
Explanation:
The electronic configuration of Magnesium () is . There are electrons in the outermost shell (). Since , the valency is equal to the number of valence electrons, which is . Magnesium tends to lose these electrons to achieve a stable octet.
Problem 2:
Determine the valency of Oxygen () given its atomic number is .
Solution:
Explanation:
The electronic configuration of Oxygen () is . It has valence electrons (). Since , the valency is calculated as . Therefore, . Oxygen needs to gain electrons to complete its octet.
Problem 3:
Find the valency of Argon () with atomic number .
Solution:
Explanation:
The electronic configuration of Argon () is . The outermost shell () is completely filled with electrons. Because it already possesses a stable octet, its combining capacity or valency is .