se calculeaza numarul de moli cu relatia niu=m./M .apoi, N= niuxNA, unde N,A este numarul lui Avogadro
M,S= 32g/mol---> niu= 32/32 mol=1mol
N,atomi= 1x6.023x10²³atomi= 6,023x10²³ atomiS
SAU
1mol...........32g
x..................32g
x=1mol
1mol contine N,Aatomi
1mol..................N= N,A=6,023x10²³atomi
M,He=4g/mol
niu= m/M= 4/4 mol=1mol
N=niuxN,A= 6,023X10²³atomi
