Question

Consider group 5A elements: nitrogen, phosphorus and arsenic. These elements show an increase in their atomic numbers. Which element has the highest ionization energy?

Answer 1

We know that the amount of energy which is required to remove an electron from an isolated gaseous atom or a molecule is known as ionisation energy or ionisation potential. Ionisation energy gives an idea about the chemical reactivity of atoms or molecules.

Complete solution:
We know that the amount of energy which is required to remove an electron from an isolated gaseous atom or a molecule is known as ionisation energy or ionisation potential. Ionisation energy gives an idea about the chemical reactivity of atoms or molecules.
We know that the atomic number increases as we move from left to right in the periodic table. As the atomic number increases ionisation energy increases.
Down the group from top to bottom, the ionisation energy decreases.
We can decide the order of ionisation energies of the given elements nitrogen, phosphorus and arsenic from their positions in the periodic table.
Now, we know that nitrogen, phosphorus and arsenic belong to the group 5A of the periodic table. These elements show an increase in their atomic numbers. Thus, nitrogen lies at the topmost. Below nitrogen lies phosphorous and below phosphorous lies arsenic.
Now, we know that down the group from top to bottom, the ionisation energy decreases.
Thus, the increasing order of ionisation energy is as follows:
Arsenic < phosphorus < nitrogen
Thus, the element having the highest ionization energy is nitrogen.

Note: There are types of ionisation energy: First ionisation energy, second ionisation energy and third ionisation energy. The amount of energy required to remove the first electron is known as the first ionisation energy. The amount of energy required to remove the second electron is known as the second ionisation energy. The amount of energy required to remove the third electron is known as the third ionisation energy.