Question

Which of the following elements has the lowest electronegativity?
(A) F
(B) Cl
(C) Br
(D) l

Answer 1

Hint: Electronegativity is the tendency of an atom to attract electrons. By looking at the valence shell and the effective nuclear charge, we can determine the electronegativity of an element. The electronegativity increases as we go from left to right and decreases as we go from top to bottom in the periodic table.

Complete step by step answer:
The electronegativity of an element can be defined as the measure of the tendency of atoms, of that element to attract the electrons towards itself during the formation of the bond.
Moving down the group, the electronegativity of the halogen group decreases. Moreover, the electronegativity of an atom is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus. The higher the associated electronegativity number, the more an element or compound attracts electrons towards itself.
There are general trends in the periodic table which you can use to determine the relative electronegativity for different elements. They are as shown:

Therefore, in a group, as the size increases, the ability to attract electrons decreases due to decrease in the effective nuclear charge. So, iodine has the lowest electronegativity. Fluorine has the highest electronegativity followed by chlorine, bromine and then with the least reactivity we have iodine,amongst the given options.

Hence, option D is correct.

Note: The noble gases i.e. group 18 elements have no electronegativity. This is because they already have eight electrons in their outermost shell and they don’t want to attract any more electrons. Since electronegativity measures the amount of attraction between an atom and an electron, and these elements will not react to form molecules and thus will not be in a situation where they can attract a pair of electrons within a molecule and that’s why noble gases do not have electronegativity.