Question

In which of the following element blocks does the atomic radius generally not tend to increase when moving down within a group?

s block
p block
d block
The atomic radius generally increases when going down a group in all of the above element blocks.

Answer 1

The d block elements show an exception in the trend of increasing atomic radius down a group due to the lanthanide contraction, while the atomic radius typically increases down a group for s block, p block, and f block elements.

Step-by-step explanation:

The student has asked about the element blocks where the atomic radius does not tend to increase when moving down within a group. The atomic radius generally increases down a group in all the blocks, including the s block, p block, and f block. However, there is a unique trend within the d block elements. In the d block, also known as the transition metals, the atomic radius does not always increase smoothly down a group. This is due to the lanthanide contraction, where the filling of the f orbitals does not screen the increasing nuclear charge effectively, leading to a smaller increase in atomic size or even a slight decrease.

Across a period, from left to right, the atomic radius decreases as the number of protons (and hence the nuclear charge) increases, and the valence electrons are added to the same principal energy level. This causes a stronger attraction between the positively charged nucleus and the electrons, consequently, decreasing the atomic size.