Question

Which of the following cation does not exist?
A. \[NH_4^ + \]
B. \[{H^ + }\]
C. \[ScO_2^ + \]
D. \[{H_3}{O^ + }\]

Answer 1

Hint: We have to know that the atom or the groups of atoms carry one or more negative or positive electrical charges. And these are known as ions. These ions are mainly in two types which are cations and anions. If the ions carry the positive charges, such types of ions are known as cation and if the ions contain the negative charge, then the ion is known as anion. Thus, the ions are a charged species.

Complete answer:
The \[NH_4^ + \] cation can exist. Because, \[NH_4^ + \] is formed by adding a hydrogen ion or proton to the lone pair of electrons present in the ammonia molecule. Hence, the option (A) is incorrect.
The hydrogen ion (\[{H^ + }\]) is formed by losing an electron from the hydrogen atom. Therefore,\[{H^ + }\] ions exist. Hence, the option (B) is incorrect.
\[ScO_2^ + \] Cation does not exist. Because, the cation is formed by the loss of one or more electrons and it contains more electrons and protons. Then the compound contains a net positive charge. Here, the scandium cannot lose two electrons to form the cation. Because, the electronic configuration of scandium is \[\left[ {Ar} \right]3{d^1}4{s^2}\].
Now it has a stable electronic configuration. If it loses two electrons, it may lead to destabilization. The scandium has to lose three electrons to attain a noble gas configuration. So, it does not form a \[ScO_2^ + \]cation. Hence, the option (C) is correct.
The \[{H_3}{O^ + }\] ion can exist. And it is formed by the combination of hydrogen with water.

So, the correct answer is “Option C”.

Note:
We have to know that when an atom or a compound gains or attracts the electron from another atom, there is a formation of negative charge. Hence, the compound becomes an anion. In other cases, if a compound loses one or more electrons to another molecule, there is a formation of a negative charge. Then the compound becomes an anion. The anions contain more protons than the electrons. And the cation contains more protons than the electron.