Question

Increasing order of electronegativities of ${\text{F,}}\,{\text{Cl,}}\,{\text{Br}}$ and ${\text{I}}$ is:
A.${\text{F < Cl < Br < I}}$
B.${\text{I < Br < Cl < F}}{\text{.}}$
C.${\text{Br < I < Cl < F}}{\text{.}}$
D.${\text{Cl < Br < I < F}}{\text{.}}$

Answer 1

To answer this question, you should recall the trends in the periodic table. The modern periodic law developed by Moseley states that the physical and chemical properties of elements are the periodic function of their atomic number. As the size of atoms increases their electronegativity decreases.

Complete step by step solution:
The tendency of an atom in a molecule to attract the shared pair of electrons towards itself is known as electronegativity. It is a dimensionless property because it is only a tendency. We measure electronegativity on several scales. The most commonly used scale was designed by Linus Pauling. According to this scale, fluorine is the most electronegative element with a value of 4 and cesium is the least electronegative element with a value of $0.7$. Electronegativity decreases in a group on going from top to bottom.
Therefore, increasing electronegativity order is ${\text{I < Br < Cl < F}}{\text{.}}$

Hence, the correct answer to this question is option B.

Note:
Let us summarize the trends of fundamental properties of an element:
Atomic Radii and Ionic radii: The atomic radii and ionic radii of elements decrease while moving from left to right in a period.
Ionization Enthalpy: Across a period in the periodic table, ionization energy generally increases. For the trend in a group, ionization enthalpy decreases from top to bottom.
Electron gain enthalpy: Electron gain enthalpy becomes more negative as we move from left to right in a period. Electron gain enthalpy is negative when energy is released while accepting an electron. While it is positive when energy is supplied to an atom while adding an electron.