Using the formula, Number of moles = \(\frac{Number of atoms or molecules}{Avogadro number}\)

 Given: Mass of Magnessium = 6g

 Mass number of Mg = 24g/mol

Number of moles = \(\frac{mass}{Molar mass}\)

  = \(\frac{6}{24}\) = \(\frac{1}{4}\) = 0.25 mole

Thus, Number of moles = \(\frac{Number of atoms or molecules}{Avogadro number}\)

 n  =  \(\frac{N}{L}\) 

 0.25 = \(\frac{N}{(6.02\times 10\(^{23}}\) 

 N = \(0.25 \times 6.02\times 10\(^{23}\))

 N = 1.505 X 10\(^{23}\)

 N = 1.51 X 10\(^{23}\)