The mass of
is 0.185 g.
To calculate the number of moles first calculate the molar mass of
.

Molar mass of nitrogen and oxygen is 14 g/mol and 16 g/mol respectively
Thus, 
Now, number of moles can be calculated from mass and molar mass as follows:

Therefore, number of moles of 0.185 g
is 0.0042 mol.
Answer:
The elements toward the bottom left corner of the periodic table are the metals that are the most active in the sense of being the most reactive.