MCQ
An ion which has $18$ electrons in the outermost shell is
  • A
    ${K^ + }$
  • B
    $C{s^{ + }}$
  • C
    $T{h^ 4+ }$
  • $C{u^ + }$

Answer

Correct option: D.
$C{u^ + }$
d
The electronic configuration of $Cu , Th , Cs$ and $K$ are

$Cu (29)=2,8,18,1$

$C u^{+}=2,8,18$

$\operatorname{Th}(90)=2,8,18,32,18,10,2$

$T h^{4+}=2,8,18,32,18,8$

$\operatorname{Cs}(55)=2,8,18,18,8,1$

$C s^{+}=2,8,18,18,8$

$K (19)=2,8,8,1$

$K^{+}=2,8,8$

Thus, $C u^{+}$has $18$ electrons in the outermost shell.

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