Đáp án:

$8=2+6\Rightarrow $ carbon ($C$), $Z=6$, $2$ lớp electron $\Rightarrow$ chữ $C$

$2=1+1\Rightarrow$ hydrogen ($H$), $Z=1$, $1$ lớp electron $\Rightarrow$ chữ $H$

$69=63+6\Rightarrow$ europium ($Eu$), $Z=63$, $6$ lớp electron $\Rightarrow$ chữ $E$

$29=25+4\Rightarrow$ manganese ($Mn$), $Z=25$, $4$ lớp electron $\Rightarrow$ chữ $M$

$58=53+5\Rightarrow$ iodine ($I$), $Z=53$, $5$ lớp electron $\Rightarrow$ chữ $I$

$19=16+3\Rightarrow$ sulfur ($S$), $Z=16$, $3$ lớp electron $\Rightarrow$ chữ $S$

$26=22+4\Rightarrow$ titanium ($Ti$), $Z=22$, $4$ lớp electron $\Rightarrow$ chữ $T$ 

$42=37+5\Rightarrow$ rubidium ($Rb$), $Z=37$, $5$ lớp electron $\Rightarrow$ chữ $R$

$76=70+6\Rightarrow$ ytterbium ($Yb$), $Z=70$, $6$ lớp electron $\Rightarrow$ chữ $Y$ 

Mật mã: $\text{CHEMISTRY}$