a) Z=20 , A=Z+n0 = 20+20 = 40
=> simbol = ₂₀⁴⁰Ca
b) Z=9 , A=19
=> simbol = ₉¹⁹F
c) Z=13 , A=Z+n = 13+14 = 27
=> simbol = ₁₃²⁷Al
d) Z=16 , A=32
=> simbol = ₁₆³²S
