The density can be calculated using the following rule:
density = mass/volume
therefore,
volume = mass/density
we have the mass=22 mg=0.022 grams and density=0.754g/cm^3
substituting in the above equation, we can calculate the volume as follows:
volume = 0.022/0.754 = 0.0291 cm^3
The answer is 12g of Carbon
First of all, you should know the valence electron of atom.
Then add charge, In case of -ve ion & subtract, in case of +ve ion.
It is definitely a molecule