a)
Na are Z = 11 si A = 23 => n0 = 23-11 = 12
23 g...... 12x6,0225x10la23 n0
9,2 g....... a = 28,90810la23 n0
b)
Zn are Z = 30 A = 65 =>
n0 = 65-30 = 35
65 g Zn........ 35x6,0225x10la23
13 g Zn ......... b = 42,16x10la23 n0
c)
Ca are Z= 20 A = 40 =>
n0 = 40-20 = 20
40 kg Ca....... 20x6,0225x10la23
4 kg................. c = 12,045x10la23 n0