Concept:Ionization energy is the energy required to remove an electron. It depends on how strongly the positive nucleus attracts the valence electrons.
Formula:$$ Z_{\text{eff}} \text{ increases left to right across a period.} $$
Solution:- As you move from left to right across a period, protons are added to the nucleus, steadily increasing the nuclear charge.
- Electrons are simultaneously added to the same principal valence shell, which does not significantly increase the shielding effect.
- The net result is a stronger effective nuclear charge (\( Z_{\text{eff}} \)) pulling the electrons closer, meaning more energy is required to tear an electron away.
Why other options are incorrect:- Option D: While electrons increase, it is the pulling force of the positive nucleus (nuclear charge) that causes the contraction and tighter grip.
- Option A & Option B: Positrons are not involved in standard atomic structure, and neutrons have no electrostatic charge.
Quality & Fidelity Assurance:
Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.