III.
Ar = (c1%xA1+c2%xA2+c3%xA3+...+cn%xAn)/100
= (89,97x20+0,76x21+9,27x22)/100 = 20,193 u.a.m.
IV.
Ar = (c1%xA1+c2%xA2+c3%xA3+...+cn%xAn)/100
= (48,63x64+27,92x66+4,11x67+18,81x68+0,61x70)/100
= 65,48 u.a.m.
V.
Al cu Z=13 si A = 27
13p+ = 13e-
stim ca A = Z+n0 => n0 = A-Z = 27-13 = 14
K cu Z = 19 si A = 39
19p+ = 19e-
din A => n0 = 39-19 = 20
Fe cu Z = 26 si A = 56
26p+ = 26e-
din A => n0 = 56-26 = 30
