Ca
Z=20------> 20p , 20 e
A=40 20n
1mol Ca----------40g Ca
xmoli--------------20g Ca
x=20g : 40g/moli= 0,5 moli Ca
1mol Ca------------------20 . 6,023.10²³ protoni
0,5 moli Ca---------------------y p
y=0,5 . 20 . 6,023.10²³=10. 6,023.10²³=60,23 .10²³protoni
