The atomic radius of main-group elements generally increases down a group because ________.
A)effective nuclear charge increases down a group
B)effective nuclear charge decreases down a group
C)effective nuclear charge zigzags down a group
D)the principal quantum number of the valence orbitals increases
E)both effective nuclear charge increases down a group and the principal quantum number of the valence orbitals increases

Question

Quizplus · Accepted Answer

The atomic radius generally increases down a group because the principal quantum number of the valence orbitals increases. As the number of energy levels increases down a group, the valence electrons are progressively further away from the nucleus, resulting in a larger atomic radius. Effective nuclear charge does decrease somewhat down a group, but this is not the main contributing factor to the trend in atomic radius.

The Atomic Radius of Main-Group Elements Generally Increases Down a Group