Question

Which one of the following has highest ionization potential ________________:
A.$L{i^ + }$
B.$M{g^ + }$
C.$He$
D.$Ne$

Answer 1

Here, in this we are asked about the highest ionization potential among these four elements. For that we need to look at their electronic configuration first and then we can find out which element has highest or lowest ionization potential.

Complete answer: Before going to this question, let’s understand what exactly ionization potential is. Ionization potential is also known as ionization energy and it is basically the amount of energy which is required in order to remove or fetch an outermost or valence electron from its isolated atom or molecule. This requirement of minimum amount of energy is known as ionization energy or potential.
If an atom is half-filled or fully filled, then the amount of energy required will be high, since half-filled or fully filled atoms are stable. So if an atom is stable then it is tough to remove electrons from them.
Now, let’s look at the electronic configuration of the above mentioned atoms.
$L{i^ + } = 1{s^2} \\\ M{g^ + } = 1{s^2}2{s^2}2{p^6}3{s^1} \\\ He = 1{s^2} \\\ Ne = 1{s^2}2{s^2}2{p^6} \\\$
From the electronic configuration, we can see that $L{i^ + }\& He$ have the same number of electrons, that is, both of them have $2$ electrons but $He$ will have lower ionisation potential than $L{i^ + }$ as $L{i^ + }$have more number of protons, that is, $L{i^ + }$ have $3$ protons and $He$ have $2$ protons.
$Ne$is fully filled but have same number of protons and $M{g^ + }$- the outermost shell is half filled but the ionization potential of $M{g^ + }$ is lower as compared to $L{i^ + }$.
Therefore, the correct option is Option-A- $L{i^ + }$.

Note:
Ionization energy also has a unit, it is measured in $Kjmo{l^{ - 1}}$. There are several factors which can affect ionization potential such as: atomic size- larger the size of the atom easier it will be to remove the electron form it that means lesser will be the ionization potential.
Nuclear charge: more the attraction between the nucleus and the outermost shell, higher will be the ionization potential.
Number of electrons present in inner shell: more the inner electrons, less will be the ionization potential as these inner electrons act as a shield between the valence electrons and the charge of the nucleus.
Penetrating factor: power of penetration of the orbitals- $s > p > d > f$