Answer:
Assuming the Cr is existing purely as Cr, and is not bonded to another Cr atom or any other compound:
First we have to calculate the number of moles of Cr. This is the mass divided by the molecular weight, so 14.9 / 51.996. This is approx. equal to 0.287.
We then need to multiply this by Avogadro's number, which is the number of atoms in one mole. So we have 0.287 x ( 6.022 × 1023 ), which is equal to 1.73 x 1023 atoms.