Question

The largest atomic radius among the following is of:
(a) Helium
(b) Carbon
(c) Oxygen
(d) Potassium

Answer 1

The atomic radius is one of the properties associated with the elements in the periodic table.
The atomic radius decreases along the period and increases down the group.
Base on the position of given elements in the periodic table, the atomic radius can be calculated.

Complete answer: Periodic table is the representation of a total of $118$ elements arranged in the increasing order of atomic number.
These elements are arranged in the vertical columns and horizontal rows.
These vertical columns are called groups and the horizontal rows are called periods.
There is a total of $7$ periods and $18$ groups in the periodic table.
These $118$ elements are arranged according to the increasing order of atomic numbers.
Helium is an element with atomic number $2$ belonging to group- $18$ and period- $1$ .
Carbon is an element with atomic number $6$ and belongs to group- $14$ and period- $2$ .
Oxygen is an element with atomic number $8$ and belongs to group- $16$ and period- $2$ .
Potassium is an element with atomic number $19$ and belongs to group- $1$ and period- $4$ .
The atomic radius is defined as the distance between the centre of the nucleus to the outermost electron in the outermost shell.
Atomic radius increases down the group and decreases along the period.
Thus, Potassium has the highest atomic radius in the given elements.

Note:
The atomic radius decreases along the period and increases down the group.
Thus, the element group and period position must be identified clearly. The electrons entering into the same period results in the decreasing attraction on outermost electrons, resulting in the decreasing nuclear effect on outermost electrons.