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

It will be nitrogen.

The energy associated with the formation of 1 mol of gaseous cations is The ionization energy. 1 mole of electrons will form 1 mole of gaseous atoms under standard conditions. The ionization energy decreases as you go down a group on the periodic table.

Explanation:

Ionization energy is defined as the energy required to remove the most loosely bound electron from a neutral gaseous atom.

With increase in atomic number there will also occur an increase in atomic size of the atom. As a result, there will be less force of attraction between the nucleus and the valence electrons of the atom.

Hence, it is easy to remove the most loosely bound electron. Therefore, with increase in size there will occur a decrease in the size of atom.

Since, out of the given group 5A elements, arsenic is larger in size and nitrogen is the smallest. Therefore, ionization energy for nitrogen will be the highest.

Thus, we can conclude that nitrogen is the element which has the highest ionization energy.