Question

Which of the following has the lowest ionization energy?

• A. Nitrogen
• B. Fluorine
• C. Sulfur
• D. Oxygen

Answer 1

The correct option is C

Sulfur

The explanation for the correct option

(C) Sulfur

Ionization energy

• The energy needed to eject an electron from an isolated gaseous atom's outermost shell is known as the ionization enthalpy.
• It is also known as ionization energy.
• In the periodic table, the ionization energy increases when moving in a period from left to right.
• In the periodic table, the ionization energy reduces as a group goes down.

Sulfur

• In the periodic table, Fluorine $\left(\mathrm{F}\right)$ is in group $17$, Oxygen $\left(\mathrm{O}\right)$ and Sulfur $\left(\mathrm{S}\right)$ are in group $16$, and Nitrogen $\left(\mathrm{N}\right)$ is in group $15$.
• Since nitrogen should have the lowest ionization potential.
• However, nitrogen has the largest ionization potential of the four due to its highly stable half-filled electronic configuration.
• Down the group, ionization potential decreases, so the ionization potential of sulfur is lower than oxygen.
• The decreasing order of ionization energy is as follows:

Nitrogen > Fluorine > Oxygen > Sulfur

• Hence, sulfur has the lowest ionization energy.

The explanation for incorrect options

• Sulfur has the lowest ionization energy.
• Hence all other options (A), (B) and (D) are incorrect.

Therefore, the correct option is (C) Sulfur.