Question

Select the correct order of electronegativity:

• A. F > Cl > Br > I
• B. N > P > As
• C. Both (A) and (B)
• D. S > O > Se

Answer 1

The correct option is C

Both (A) and (B)

The explanation for the correct option:

Option C

Electronegativity:

• Electronegativity is the tendency of an atom to attract the shared pair of electrons towards itself in a chemical bond.
• Fluorine is the most electronegative element among all the elements.
• As we move across a period from left to right the nuclear charge increases and the atomic size decreases, therefore the value of electronegativity increases across a period in the modern periodic table.
• There is an increase in the atomic number as we move down the group in the modern periodic table. The nuclear charge also increases but the effect of the increase in nuclear charge is overcome by the addition of one shell. Hence, the value of electronegativity decreases as we move down the group.
• This concept is applicable for both options that are options A and option B.

Option A

• Fluorine($\mathrm{F}$) is the most electronegative element among all the elements.
• There is an increase in the atomic number as we move down the group in the modern periodic table. The nuclear charge also increases but the effect of the increase in nuclear charge is overcome by the addition of one shell.
• Hence, the value of electronegativity decreases as we move down the group.
• Therefore, in the halogen group, on moving down the group from fluorine($\mathrm{F}$) to astatine($\mathrm{At}$) the electronegativity value decreases.
• The order is $\mathrm{F}>\mathrm{Cl}>\mathrm{Br}>\mathrm{I}$.

Option B

• There is an increase in the atomic number as we move down the group in the modern periodic table. The nuclear charge also increases but the effect of the increase in nuclear charge is overcome by the addition of one shell.
• Hence, the value of electronegativity decreases as we move down the group.
• Nitogen($\mathrm{N}$), Phosphorous($\mathrm{P}$), Arsenic ($\mathrm{As}$) belong to the group number 15.
• On moving down the group from nitrogen to arsenic the electronegativity value decreases.
• The order is $\mathrm{N}>\mathrm{P}>\mathrm{As}$.

The explanation for the incorrect option:

Option D

• Oxygen($\mathrm{O}$) is more electronegative than sulphur ($\mathrm{S}$) and selenium($\mathrm{Se}$).
• They all belong to the same group which is group number 16 elements.
• The correct order will be $\mathrm{O}>\mathrm{S}>\mathrm{Se}$

Therefore, option C is correct.