Question

The electron affinity increases on moving from left to right along a period. Arrange the reasons in a proper sequence.
a.The amount of energy released during the addition of an electron increases from left to right along a period.
b.Effective nuclear charge of the elements increases from left to right.
c.The atomic size of the elements decreases from left to right
d.The tendency to gain electrons and form anion increases from left to right
A.a c b d
B.b c d a
C.c a d b
D.d c b a

Answer 1

Hint: To solve this question, it is important to know about the concepts discussed in the options.Effective nuclear charge can be understood as the net force of attraction the nucleus has on the valence electrons within a given atom. On the basis of that, we can derive relations between the different concepts mentioned, and accordingly find the chronology in which they make sense.

Complete step by step answer:
Before we move forward with the solution of the given question, let us first understand some important basic concepts.
The effective nuclear charge is dependent on two major factors, viz. atomic radius and shielding effect. Atomic radius determines the atomic size and goes on decreasing from left to right to right in the period. Effective nuclear charge is inversely proportional to the atomic size, i.e. it decreases as the atomic size increases.
The electronegativity of an atom is defined as the ability of an atom to attract a lone pair of electrons. As it moves from left to right in a period, the size of the atom decreases and the effective nuclear charge increases. Hence the high nuclear charge helps in attracting more negative charge in the form of electrons. Hence, the electronegativity also increases from left to right in a period.
When electrons are added to atoms with high electronegativities, the energy released is also high. This is because there is a large difference between the stable state and natural state of highly electronegative atoms. Hence, the energy released also increases with the increase in the electronegativity of the atoms.
Hence, on the basis of the information discussed above, we can arrange the given statements as:
(b) Effective nuclear charge of the elements increases from left to right.
(c) The atomic size of the elements decreases from left to right
(d) The tendency to gain electrons and form anion increases from left to right
(a) The amount of energy released during the addition of an electron increases from left to right along a period.

Hence, Option B is the correct option.

Note:
Electron affinity is a measure of the energy released when an extra electron is added to an atom. In general, electron affinities become more negative as we move from left to right on the periodic table. In general, electron affinities become less negative from top to bottom of a group.