Question

The element with highest ionization potential is:
A.Nitrogen
B.Oxygen
C.Helium
D.Neon

Answer 1

The amount of energy required to remove an electron from an isolated atom or molecule is called ionization energy. Ionization potential is energy measured in electron volts. The general trend of ionization potential in the periodic table is that on moving across a period from left to right, Ionization potential increases. On moving down the group, ionization potential decreases.

Complete step by step answer:
Now we know that ionization potential decreases down the group. Let us understand the reason
On moving down the group, the atomic number as well as the shells are also increased.
Therefore, the outermost electrons are far from the nucleus and nuclear charge. Therefore, an electron can be removed easily on moving down the group.
As the number of shells is increased, it is easier to remove the outermost electron.
On moving across a period from left to right, the atomic number increases while the size of atoms is decreased. Thus, the outermost electrons will be more close to the nucleus with increased nuclear charge. Therefore, more energy should be given to removing the outermost electron, and ionization potential increases.
Knowing these concepts and the reason, let us compare the options
On comparing all the options, there is 2 inert gas which has a filled orbital.
To remove an electron from the outer orbital of fully filled or half-filled, very high energy is to be given which makes the ionization potential highest.
The electronic configuration of He is 2 (which is in s orbital) and the electronic configuration of Neon is 2, 8.
In Helium and Neon, the octet is complete.
Now let us look at Helium and Neon.
Neon is below helium in the group. We know that on going down the group, the ionization potential decreases. Therefore, neon has less ionization potential than helium
The element with the highest ionization potential is Helium.

Thus, the correct option is C.

Note: There is some exception in the regular trends of ionization potential. For example, Oxygen has a low ionization potential that nitrogen which by the regular trend should be the opposite. This is because Nitrogen has a half-filled orbital which makes it more stable and the release of the electron is difficult. Thus the ionization energy is more for nitrogen.