Question

Which of the following elements has the lowest electronegativity? How do you know?
(A) Lithium
(B) Carbon
(C) Bromine
(D) Fluorine

Answer 1

Hint: The electronegativity of an atom is the tendency of an atom to attract the electrons present in a chemical bond toward itself.
The atoms which can accommodate electrons by gaining electrons will show the electronegative nature.

Complete answer:
In the question it is asked that from the given four options we have to say which element has the least electronegativity.
We know that the electronegativity of an atom can be explained as the tendency of that atom to attract the pair of bonding electrons towards itself in a chemical bond. In a compound if the two molecules that has undergone the chemical combination has electronegativity difference then the more electronegative atom will attract the two electrons present in the chemical bond towards itself forming a partial negative charge and the other will possess a partial positive charge and the bond acts as a polar bond.
Electronegativity is one of the periodic trends in the periodic table. And we know that the electronegativity parameter decreases as we down the group, as the size increases and the outermost electron possesses less effect even though effective nuclear charge is increasing due to the larger size of the atom. And as we move across a period the size of the atom decreases and the attraction between the outer electrons are increasing because of the increase in effective nuclear charge and the electronegativity also increases when we move from left to right of the period.
Now let’s solve this problem, we know that the electronegative atom attracts the electrons towards itself and is accommodated in the valence shell. An atom always tends to attain a stable configuration of noble gas i.e. It tends to attain the octet configuration.
 If we see the four options, Li have one valence electron in its valence shell and it always tends to lose that electron to attain the stable configuration and shows least electronegativity whereas in the next option is carbon, here carbon have a valency of 4, Br has 7 valence electrons and F also has 7 valence electrons and these three atoms can accommodate electrons in its valence shell and complete its octet so they possess higher electronegativity than Li.
Therefore the correct option for the question is option (A) Lithium.

Note: Another way of approaching this question is comparing the other options with F atoms. We know that the F is the most electronegative atom in the electronegativity chart. And if we move towards the left of the F atom in the period along a period the electronegativity decreases and if we move down the group the electronegativity decreases down the group.
Li, C and F belong to the same period and Br belongs to the same group of that of F. If we compare the positions of atoms the Li is in the farthest from F and it will be the least electronegative atom in the given options.