Question

Atomic radius of carbon and oxygen is 67 pm and 48 pm. The atomic radius of nitrogen is:
(A) 69 pm
(B) 45 pm
(C) 56 pm
(D) None of the above

Answer 1

Hint: To solve this question, understand the nature of the trends observed in a periodic table within a given period. On the basis of these relations, derive the value for the atomic radius of oxygen

Complete Step-by-Step Answer:
The elements that are given to us, namely carbon, nitrogen and oxygen, all of them belong to the same period in the periodic table.

As we can see, the elements are arranged according to their atomic numbers in the periodic table. As we move from left to right in a period, the atomic number increases. By this definition, we can that the atomic number of carbon is less than nitrogen is less oxygen.
Like this, various other trends are followed as we move from left to right in a period. Some of these trends include decrease in atomic radius, increase in electronegativity, increase in atomic masses, etc. the one trend that would help us in solving this question is that of decreasing atomic radii.
As we move from left to right in a period, the atomic radius of elements keeps on decreasing. This means that the relation between the atomic radii of carbon, nitrogen and oxygen would be:
Carbon > nitrogen > oxygen
Now, we are already given the values for atomic radii of carbon and oxygen. Hence,
67 pm > nitrogen > 48 pm
From the given options, the only value which satisfies this condition is 56 pm

Hence, Option C is the correct option.

Note: The number of energy levels increases as you move down a group as the number of electrons increases. Each subsequent energy level is further from the nucleus than the last. Therefore, the atomic radius increases as the group and energy levels increase. As you move across a period, atomic radius decreases.