Question

The electron affinity values for the halogens show the following trend:
A.) F < Cl > Br > I
B.) F < Cl < Br < I
C.) F > Cl > Br > I
D.) F < Cl > Br < I

Answer 1

Hint: Electron affinity is the change in energy of a neutral atom when an electron is added to it. The electron affinity order of halogens shows an interesting trend, in which an element has significantly higher electron affinity than others.

Complete step by step answer:
Electron affinity of an atom or molecule is defined as the total energy released when an electron is added to a neutral atom or molecule in its gaseous state to form a negative ion. Since the atomic size increases down the group, the electron affinity generally decreases down the group as the electron will not be as attracted to the nucleus when the size increases, resulting in a low electron affinity.
In the case of halogens, however, fluorine has a lower electron affinity than chlorine. This can be explained by the small size of fluorine as compared to chlorine. Because of this, any new electron trying to attach to fluorine experiences lower electron affinity from the electrons already living in the element's 2p orbital.

Hence, the correct order of electron affinity for the halogens is (A) F < Cl > Br > I

Note: Remember that chlorine has the highest electron affinity in the modern periodic table. As electron affinity increases along a period, so the group 17 elements have the highest electron affinity.