Răspuns:
Magneziu Mg Z=12, A=24, p=12, n=12, e=12, 1s2 2s2 2p6 3s2
Aluminiu Al Z=13, A=27, p=13, n=14, e=13, 1s2 2s2 2p6 3s2 3p1
Litiu Li Z=3, A=7, p=3, n=3, e=3, 1s2 2s1
Potasiu K Z=19 A=39, p=19, n=20, e=19, 1s2 2s2 2p6 3s3 3p6 4s1
Explicație:
