How many nitrogen atoms are present in 0.150 mol of zn(no3)2?

First calculate number of Nitrogen atoms contained by 1 mole of Zn(NO₃)₂,

As one formula unit of Zn(NO₃)₂ contains 2 Nitrogen atoms, then one mole of Zn(NO₃)₂ will contain,

                           =  2 × 6.022 × 10²³

                           =  1.20 × 10²⁴ Atoms of Nitrogen / mole

Now, calculate number of Nitrogen Atoms in 0.150 moles of  Zn(NO₃)₂.
As,
 1 mole of  Zn(NO₃)₂ contained  =  1.20 × 10²⁴ atoms of N
Then,
0.15 mole of  Zn(NO₃)₂ will contain  =  X atoms of N
Solving for X,

                                    X  =  (0.15 mol × 1.20 × 10²⁴ atom) ÷ 1 mol

                                    X  =  1.80 × 10²⁴ Atoms of Nitrogen
Result:
           So, 0.15 mole of  Zn(NO₃)₂ contains 1.80 × 10²⁴ atoms of Nitrogen.

The answer to that would be magnesium