Question

Cs atoms are the largest naturally occurring atoms. The radius of Cs atom is $2.6\mathring{A}$. The number of moles of Cs atoms to be laid side by side to give a row of Cs atoms 2.50 cm long is $x\times {10}^{-17}$. The value of x is

Answer 1

Diameter of Cs$=2\times 2.6=5.2\mathring{A}=5.2\times {10}^{-8}cm$

Number of atoms in 2.50 em row =$\frac{2.50}{5.2}\times {10}^{-8}$

$=0.48\times {18}^8$

$=4.8\times {10}^{7}Csatoms$

$\therefore$Moles of Cs atoms = $\frac{4.8\times {10}^7}{6}\times 10623=0.8\times {10}^{-16}$

$=8\times {10}^{-17}$

$\therefore x\times {10}^{-17}=8\times {10}^{-17}$

$\Rightarrow x=8$