Bài `17`:

`@` `A`, `B` `in` 1 nhóm, 2 chu kì liên tiếp

TH1: `p_A - p_B = 8`

`=>` \(\left[ \begin{array}{l}p_A = (32 + 8) : 2 = 20\\p_B = (32 - 8) : 2 = 12\end{array} \right.\) 

`=>` \(\left[ \begin{array}{l}A = Calcium\\B = Magnesium\end{array} \right.\) 

TH2: `p_A - p_B = 32`

`=>` \(\left[ \begin{array}{l}p_A = (32 + 32) : 2 = 32\\p_B = (32 - 32) : 2 = 0\end{array} \right.\) 

`=>` TH2 loại

Vậy \(\left[ \begin{array}{l}A = Calcium\\B = Magnesium\end{array} \right.\) 

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