Question
Question: The correct decreasing order of atomic radii of group 13 element is...
The correct decreasing order of atomic radii of group 13 element is
A
B > Al > Ga > In > Tl
B
B > Ga > Al > In > Tl
C
Tl > In > Al > Ga > B
D
In > Tl > Ga > Al > B
Answer
Tl > In > Al > Ga > B
Explanation
Solution
Atomic radii generally increase down a group due to the addition of new electron shells. However, in Group 13, Gallium (Ga) has a smaller atomic radius than Aluminum (Al) due to the poor shielding effect of the filled 3d orbitals in Ga, which leads to an increased effective nuclear charge. Thus, the increasing order of atomic radii is B < Ga < Al < In < Tl. Reversing this gives the decreasing order: Tl > In > Al > Ga > B.