Question

How do you calculate the electronegativity of an element?

Answer 1

Hint Electronegativity is the ability of an atom in a chemical compound to attract electrons or electron density toward itself within a covalent bond. Electronegativity depends upon the force of attraction between the nucleus and bonding electrons in the outer shell. Electronegativity of any given element is not constant. It varies according to the element to which it is bound. It is not a measurable quantity. It is only a relative number.
Electronegativity of an element is determined through Mulliken scale, and electronegativity difference of two elements is calculated through polling scale. Allred Roschow's scale is also used to calculate the electronegativity of an atom.

Complete Step by step solution:
(i) Electronegativity was first explained by polling. Polling calculated electronegativity difference between two atoms in a chemical bond on the bases of bond energy or resonance energy of the atoms.
According to polling scale
$${\text{X}}_{\text{A}}\text{-}{\text{X}}_{\text{B}}\text{=0}\text{.208}\sqrt{\mathrm{\Delta }\text{ AB}}$$
Here $\mathrm{\Delta }AB$ is the resonance of the molecule AB.
 (ii) According to Mulliken electronegativity is average value of ionisation potential (minimum energy required to remove most loosely bounded outermost shell electron in ground state from an isolated gaseous atom) and electron affinity (energy release when an electron is added to natural isolated gaseous atom) of an element.
$${\text{X}}_{\text{M}}\text{=}{\displaystyle \frac{\text{Ionisation potential+Electron affinity}}{\text{2}}}$$
 Here, ${\text{X}}_{\text{M}}$ represents the electronegativity of an element ‘M’.
(iii) As per Roschow’s, electronegativity is the force by which the nucleus of an atom attracts electrons which are on the covalent radius(r).
$${\text{X}}_{\text{(AR)}}\text{ Electronegativity =}{\displaystyle \frac{{\text{Z}}_{\text{effe}}\times {\text{e}}^{\text{2}}}{{\text{r}}^{\text{2}}}}$$
Where ${\text{Z}}_{\text{effe}}$ denotes the effective nuclear charge of the atom and ‘r’ denotes the radius of the atom.

Note: Small atoms are normally having more electronegativity than the larger atoms. Electronegativity of an element is unit less quantity. Electronegativity regularly increases in a period because moving in the period size or radius of the element decreases regularly and electronegativity does not depend on electronic configuration of element.