Đáp án:

Giải thích các bước giải:

 O =1s2 2s2 2s4

O 2- =1s2 2s2 2p6

S =1s2 2s2 2p6 3s2 3p4

S2-=1s2 2s2 2p6 3s2 3p6

Cl=1s2 2s2 2p6 3s2 3p5

Cl-=1s2 2s2 2p6 3s2 3p6 

K =1s2 2s2 2p6 3s2 3p6 4s1 

K+ =1s1 2s2 2p6 3s2 3p6 

Ca = 1s2 2s2 2p6 3s2 3p6 4s2

Ca2+ =1s2 2s2 2p6 3s2 3p6

Fe=1s2 2s2 2p6 3s2 3p6 4s2 4d6

Fe2+=1s2 2s2 2p6 3s2 3p6 4s2 4d4

Fe3+=1s2 2s2 2p6 3s2 3p6 4s2 4d3

Em tham khảo nha :

\(\begin{array}{l}
Che\,O:1{s^2}2{s^2}2{p^4}\\
Che\,{O^{2 - }}:1{s^2}2{s^2}2{p^6}\\
Che\,S:1{s^2}2{s^2}2{p^6}3{s^2}3{p^4}\\
Che\,{S^{2 - }}:1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}\\
Che\,Cl:1{s^2}2{s^2}2{p^6}3{s^2}3{p^5}\\
Che\,C{h^ - }:1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}\\
Che\,K:1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^1}\\
Che\,{K^ + }:1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}\\
Che\,Ca:1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}\\
Che\,C{a^{2 + }}:1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}\\
Che\,Fe:1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^6}\\
Che\,F{e^{2 + }}:1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^6}\\
Che\,F{e^{3 + }}:1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^5}
\end{array}\)