Chemistry S & P Block Elements BUMHS 2022
PMDC Verified Question 57 of 104
Which of the following has the least ionization potential?
A
He
B
Li
C
Zn
D
N
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Li
Concept:

Ionization potential (or ionization energy) is the energy required to strip the most loosely bound electron from a gaseous atom. It is lowest for Group 1 metals.

Solution:

  • Lithium (Li) is an alkali metal (Group 1). Its electronic configuration is \( 1s^2 2s^1 \).
  • It readily loses its single valence electron to achieve the stable noble gas configuration of Helium (\( 1s^2 \)).
  • Due to this strong driving force and large relative size compared to non-metals, Li has the least ionization potential among the given choices.


Why other options are incorrect:

  • He: A noble gas with a full shell. It has the highest ionization energy in the entire periodic table.
  • N: A non-metal with a half-filled, very stable p-orbital (\( 2p^3 \)), resulting in high ionization energy.
  • Zn: A transition metal with a fully filled d-subshell (\( 3d^{10} 4s^2 \)), giving it a relatively high ionization potential compared to Li.

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