Question

How can we know which elements are more electronegative than others? I’ve never come across any such formula or trick for this, except learning it by practice. Please tell if you know any.

Answer 1

Hint: Electronegativity is the tendency of attraction of a shared pair of electrons towards itself. Since the electronegative compounds attract the electron pair towards itself, they tend to gain more negative charge.

Complete step by step answer:
Fluorine is the highest electronegative element and group-17 exhibits high electronegativity among all groups in the periodic table.
Electronegativity varies according to some trends in the periodic table. Generally, electronegativity increases from left to right across the period and it decreases down the group in the periodic table.
On moving down the group, the size of the atom increases, and it leads to a decrease in the attraction of the nucleus and outermost electron (effective nuclear charge). This leads to a decrease in electronegativity and also, electronegativity is directly proportional to the effective nuclear charge.
On moving from left to right across the period, the atomic size is increased by one unit and it won't make any dramatic change. Thus. Electronegativity increases from left to right across the periodic table.
And also, most nonmetals tend to be more electronegative in nature and it readily gains an electron to form an anion. Let us consider a non-metal element - “Chlorine”. The outermost electronic configuration of chlorine is $$3s^{2}3p^5$$. Chlorine only needs one electron to attain octet –stable configurations. So, it mainly focuses on adding one electron to attain an octet configuration instead of removing its valence of five electrons.
Thus, chlorine is electronegative in nature.

Note: Mulliken and Pauling's scales are used to measure the electronegativity of the given element. In Pauling's scale, electronegativity can be calculated by using the formula,
$$X_A-X_B=0.208\sqrt{D}$$
Where,
$$X_A$$-Electronegativity of A in A-B bond
$$X_B$$- Electronegativity of B in A-B bond
D-electronegativity difference
In Mulliken's scale, electronegativity can be calculated as the average of electron affinity and ionization energy of the given element.