Answer
Two atoms of lead.
Work Step by Step
Molar mass of Pb (lead)=$207.2\,g/mol$
That is, the mass of $6.022\times10^{23}$ Pb atoms is equal to 207.2 g.
$\implies$ mass of 1 Pb atom=$\frac{207.2\,g}{6.022\times10^{23}}=3.441\times10^{-22}\,g$
Then, the mass of 2 Pb atoms=
$2\times3.441\times10^{-22}\,g=6.882\times10^{-22}\,g$
Mass in grams of He=
$n\times \text{Molar mass of He}$
$=5.1\times10^{-23}\,mol\times4.0026\,g/mol$
$=2.041\times10^{-22}\,g$
Greater mass is for two atoms of Pb.
