Question

Which element has the higher ionization energy; boron or oxygen?

Answer 1

Hint: Ionization energy which is also termed as ionization enthalpy is the minimum amount of energy required to remove the mostly loosely attached electron of an isolated neutral gaseous atom or molecule.

Complete answer:
Ionization energy is the energy required for withdrawing the loosely bounded electron from a gaseous atom or ion. Ionization energy of each ion can be calculated. The basic equation of ionization energy is:
 $X+X^{+}+e^{-}$
When the electrons are removed from the molecule or the atom, the energy needed to remove the other electrons from the same atom or molecule, the equation will change because the amount of energy required to remove electrons is changed.
On moving down the periodic table, the ionisation energy generally decreases as the atomic radius of the elements increases, thus it becomes easier to remove the electron that is far from the nucleus. Whereas on moving left to right within a period, the ionization energy increases as the atomic radius decreases which makes it harder to remove the electron that is closer to the nucleus.
Here in this question, there are two elements which are: $Boron$ and $Oxygen$ whose atomic number is:
 $B,$
 $Z=5$
 $O,$
 $Z=8$
Here oxygen and boron are in the same period but the boron is in $13$ group whereas oxygen is in $16$ group which indicate that the atomic radius of boron is greater than oxygen so the ionisation energy of oxygen is higher than boron moreover the atomic number of oxygen is higher than boron so the ionization energy of oxygen is higher than boron.

Note:
The ionization energy also determines the closeness of the electron from its nucleus. The closer the electron is to the nucleus , the more ionization energy required. Basically, the atomic radii increase and the ionization energy decreases and vice versa.