Chemistry

Question Analysis
This question evaluates the understanding of periodic trends, specifically the trend in atomic radius across a period.

Key Concept Explanation
Atomic radius generally decreases as you move from left to right across a period due to the increasing nuclear charge, which pulls the valence electrons closer to the nucleus.
In Period 6, this trend is observed, and the lanthanide contraction also plays a role, making the atomic radii of lanthanides smaller than expected.

Step-by-step Solution
1. Identify the elements in Period 6: Cesium (Cs), Barium (Ba), Lanthanum (La), and Cerium (Ce).
2. Compare their positions in the periodic table:
Cesium (Cs) is in Group 1.
Barium (Ba) is in Group 2.
Lanthanum (La) is in the Lanthanide series.
Cerium (Ce) is also in the Lanthanide series, but it is further to the right.
3. Appl...