#1 mol = 6.022 xx 10^(23)# particles
#rArr 6.022 xx 10^(23)#atoms of #Sn# #= 1mol# of #Sn#
#rArr 1# atom of #Sn# # = 10^(-23)/6.022 mol# of #Sn#
#rArr3620# atoms of #Sn# #= 3620xx10^(-23)/6.022mol# of #Sn#
#:. 3620# atoms of #Sn# #= 6.01xx10^(-21)mol# of #Sn#