Question

Give the trends in the following properties of Halogens- Electron affinity.

Answer 1

Halogens:

• Halogens belong to group 17 of the periodic table. and valence electrons of group 17 are 7.
• General electronic configurations of ns²np⁵ are called Halogens. They include Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At).

Electron Affinity:

• Electron affinity is the amount of energy released when an electron is added to the outermost shell of one mole of an isolated gaseous atom in its lower energy state.
• Or, Electron affinity is the energy released while converting a neutral gaseous isolated atom into a negatively charged gaseous ion by the addition of electrons.
  

Electron affinity trend:

• On moving from left to right in a period of the periodic table, the atomic size decreases, and the nuclear charge increases. Thus, the electron affinity increases.
• On moving down the group in the periodic table, the atomic size increases, and the nuclear charge decreases. Thus, the electron affinity decreases.

The trend of Electron Affinity of Halogens:

• In general, as the size of the atom increases down the group, the electron affinity decreases.
• As all the halogen atoms lack only 1 electron in their valence shell to achieve the stable completely filled electronic configuration, thus they readily accept the additional electron to achieve that stable configuration.
• Exception: But in the case of halogens, Fluorine has less electron affinity than Chlorine due to the compact size of the fluorine atoms which do not want to accommodate any more electrons. On the other hand, Chlorine has 3p orbitals which are bigger in size to accept the additional electron.
• Hence, the increasing order of Electron Affinity of halogens is: At <I < Br < F < Cl