Answer
Ti has the greatest number of atoms
Work Step by Step
Number of mole = $\frac{mass}{molar mass} $
a) Number of mole = $\frac{27.2g}{52g/mol} = 0.52$ mole of Cr
b) Number of mole = $\frac{55.1g}{48g/mol} = 1.147$ mole of Ti
c) Number of mole = $\frac{205g}{207g/mol} = 0.99$ mole of Pb
Ti has the greatest number of moles, therefore, has the greatest number of atoms as well.
