Question

Which element has the highest first ionization potential?

• A. N
• B. Ne
• C. He
• D. H
• E. Li

Hint:

Helium holds the record for the highest first ionization potential of all elements in the periodic table.

Answer 1

The Correct Option is C

Concept: Ionization Potential (or Ionization Energy) is the energy required to remove the most loosely bound electron from an isolated gaseous atom.
• It generally increases across a period (left to right) due to increasing nuclear charge.
• It generally decreases down a group due to increasing atomic size and shielding effect.
• Noble gases have exceptionally high ionization potentials because of their stable, fully filled electronic configurations.

Step 1: Compare the positions in the periodic table.

• He (Helium): Period 1, Group 18.
• H (Hydrogen): Period 1, Group 1.
• Ne (Neon): Period 2, Group 18.
• N (Nitrogen): Period 2, Group 15.
• Li (Lithium): Period 2, Group 1.

Step 2: Evaluate the effect of shell and stability.
Helium has its only shell ($n=1$) completely filled with two electrons ($1s^2$). Because the electrons are very close to the nucleus and the configuration is extremely stable, it requires the most energy to remove an electron. While Neon also has a stable octet, its valence electrons are in the second shell ($n=2$), further from the nucleus than Helium's, making them slightly easier to remove than Helium's.