Select the more electronegative element in each pair. a. f br b. s o c. n p d. k ca

a. F

b. O

c. N

d. Ca

Explanation:

Electronegativity is the tendency of an atom in a bond pair to attract the shared pair of electron towards itself.

Low ionization energies as well as low electron affinities mean the atom has low effective nuclear charge, which results in the less attraction of the valence electrons by the atom and thus, low electronegativity.

Across the period, there is an increase in effective nuclear charge and thus there is more force of attraction between the nucleus and the valence electrons when moving left to right in a period.  Thus, electronegativity increases across the period.

Down the group, there is an increase in number of shells and thus the distance between the nucleus and the valence electron increases.  Thus, electronegativity decreases down the group.

(a) Out of F and Br, they are the members of the same group and electronegativity decreases down the group. Thus, F is more electronegative element.

(b) Out of O and S, they are the members of the same group and electronegativity decreases down the group. Thus, O is more electronegative element.

(c) Out of N and P, they are the members of the same group and electronegativity decreases down the group. Thus, N is more electronegative element.

(d) Out of K and Ca, they are the members of the same period and electronegativity increases across the period. Thus, Ca is more electronegative element.