Which of the following best describes the shielding effect in atoms?

• A. The tendency of atoms to lose electrons and form positive ions.
• B. The attraction between the nucleus and valence electrons that increases across a period.
• C. The reduction in effective nuclear charge experienced by outer electrons due to the repulsion from inner electrons.
• D. The increase in atomic radius as electrons are added to the same energy level.

Answer: (C)

Verified step by step guidance

1. Understand that the shielding effect refers to how inner (core) electrons reduce the attraction between the nucleus and the outer (valence) electrons.
2. Recognize that inner electrons repel outer electrons, which decreases the effective nuclear charge felt by the valence electrons.
3. Note that this reduction in effective nuclear charge means valence electrons are held less tightly by the nucleus.
4. Distinguish the shielding effect from other concepts such as atomic radius changes or ionization tendencies, which are related but different phenomena.
5. Conclude that the best description of the shielding effect is: 'The reduction in effective nuclear charge experienced by outer electrons due to the repulsion from inner electrons.'