Order the following atoms from smallest to largest atomic radius: C, N, P

N ∠ C ∠ P

Explanation:

Atomic radius:

It is define as the distance from nucleus of an atom the outer most electronic shell.

As we move down the group atomic radii increased because of increase of atomic number.  Electrons are added in next level cause the atomic radii to increased. The hold of nucleus on valance shell become weaker because of shielding of electrons thus size of atom increased.

When we move from left to right across the periodic table electron are added in the same shell at the same time protons are also added in the nucleus hence positive charge is going to increase and this effect lead to the greater nuclear attraction. The electrons are pull towards the nucleus and valance shell get closer to the nucleus and atomic radii decreases.

Carbon and nitrogen are present in period 2 while phosphorus is present in period 3 thus phosphorus has largest atomic radii. Carbon and nitrogen are present in same period but nitrogen is more right as compared to the carbon which means nitrogen has one more valence electron thus its size is smaller than carbon.

Values of atomic radii.

P = 98pm

C = 67pm

N = 65 pm

N ∠ C ∠ P

the answer is barium and copper bromide