Question

Based on their positions in the periodic table, list the following atoms in order of increasing radius: Sr, Ca, Si, Cl.

Short answer

$Cl<Si<Ca<Sr$

Step-by-step solution

Atomic radius of the elements along the period from left to right in the periodic table

As the effective nuclear charge increases along the period from left to right in the periodic table, the atomic radius of the elements of the same period decreases.

Atomic radius of the elements along with the group from top to bottom in the periodic table

If the elements of the same (column) group are considered in the periodic table, the new shell will enter the atoms, increasing the atomic radius.

The order of radius in the given elements 

The element Sr belongs to the fifth period. So it has the largest size.

The element Ca belongs to the fourth period. So it has the second-largest size.

The elements Si and Cl belong to the third period. But from left to right along the period, atomic size decreases.

Thus, the order is:

$Cl<Si<Ca<Sr$