Question

Mention the compounds in which $d-$ subshell electrons are taking part in chemical reaction during their formation.
$XC{l}_2,X{O}_2,X_2{O}_7$

Answer 1

$XC{l}_2-ion{X}^{2+}$ (electrons in $4s$ only)

$X{O}_2-ionX{+}^4$ ($2$ electrons in $4s$ and $2$ electrons in $3d$)

$X_2{O}_7-ion{X}^{7+}$ ($2$ electrons in $4s$ and $5$ electrons in $3d$)

$X{O}_2,X_2{O}_{7}d-$ subshell electrons are taking part in chemical reaction during the formation of $X_2{O}_7$