Question

An ion has 18 electrons in the outermost shell, it is

• A. $Cu^+$
• B. $Th^{4+}$
• C. $Cs^+$
• D. $K^+$

Answer 1

Answer: (A)

$Cu^+$

Answer 2

The electronic configuration of Cu, Th, Cs and K are
Cu(29) = 2, 8,18,1
$Cu^+$ = 2, 8,18
Th(90) = 2, 8,18, 32,18,10, 2
$Th^{4+}$ = 2, 8,18, 32,18, 8
Cs(55) = 2, 8,18,18, 8,1
$Cs^+$ = 2, 8,18,18, 8
K(19) = 2, 8, 8,1
$K^+$ = 2, 8, 8
Thus, $Cu^+$ has 18 electrons in the outermost shell.

An ion with 18 electrons in the outermost shell can be one of several possibilities, depending on whether the ion has gained or lost electrons.

If the ion has gained electrons, it would have more than 18 electrons in the outermost shell, and would therefore have a negative charge. The most likely ion with 18 electrons in the outermost shell and a negative charge would be the chloride ion (Cl-), which has a total of 18 electrons in its outermost shell.

If the ion has lost electrons, it would have fewer than 18 electrons in the outermost shell, and would therefore have a positive charge. The most likely ion with 18 electrons in the outermost shell and a positive charge would be the argon ion (Ar+), which has 17 electrons in its outermost shell. If the argon atom were to lose one electron, it would have 18 electrons in the outermost shell and a net positive charge of +1.

However, it's important to note that the specific ion with 18 electrons in the outermost shell depends on the context of the problem and the specific elements involved.