Which element experiences a greater shielding effect: bromine (Br) or chlorine (Cl)?

• A. Both experience the same shielding effect because they are in the same group.
• B. Bromine, because it has more inner electrons that shield the valence electrons from the nucleus.
• C. Chlorine, because it has a higher atomic number and thus more shielding.
• D. Neither, because shielding does not change across a period.

Answer: (B)

Verified step by step guidance

1. Understand the concept of shielding effect: Shielding occurs when inner (core) electrons reduce the effective nuclear charge felt by the outer (valence) electrons. More inner electrons mean greater shielding.
2. Identify the positions of bromine (Br) and chlorine (Cl) on the periodic table: Both are in Group 17 (halogens), but bromine is in Period 4, while chlorine is in Period 3.
3. Compare the number of inner electrons: Bromine has more electron shells (4 shells) than chlorine (3 shells), so bromine has more inner electrons that can shield the valence electrons.
4. Analyze how this affects shielding: Since bromine has more inner electrons, it experiences a greater shielding effect, reducing the effective nuclear charge felt by its valence electrons compared to chlorine.
5. Conclude that shielding increases down a group due to the addition of electron shells, so bromine experiences a greater shielding effect than chlorine.