Question

The correct order of ionization energy of li+, Be+, B+, C+, N+, O+, F+

Answer 1

Answer:

The correct order of ionization energy is Li⁺∠B⁺∠Be⁺∠C⁺∠O⁺∠N⁺∠F⁺

Explanation:

The minimum energy required to remove an electron from an isolated gaseous atom in its ground state is called the ionization enthalpy.

It is the quantitative measure of the tendency of an element to lose an electron. The energy required to remove the most loosely bound electron from an isolated gaseous atom is called the first ionisation enthalpy.

On moving along the period from left to right, the successive addition of one electron results in an increased nuclear charge. Since the electrons are added to orbitals of the same principal quantum level, the shielding effect remains the same and is not enough to compensate for the increased nuclear charge. Thus, the increasing nuclear charge outweighs the shielding effect across the period. As a result, the outermost electrons are held more and more firmly and hence, the ionisation energy increases across a period.

Across the period, the ionisation energy increases due to a decrease in atomic size. But the first ionisation energy of nitrogen is greater than that of oxygen. It is due to the more stable electronic configuration of nitrogen(half-filled configuration) that it is more difficult to remove an electron from nitrogen than from oxygen. Thus, oxygen has lower ionisation energy than nitrogen.

Also, Beryllium has a higher ionisation enthalpy than boron. In both cases, the electron to be removed belongs to the same principal shell. In Be(1s² 2s²), it is 2s-electron while in B(1s² 2s² 2p¹), it is 2p-electron. The penetration of a 2s-electron to the nucleus is more than that of a 2p-electron. The 2s-electrons are more strongly attracted by the nucleus than the 2p-electrons. A higher amount of energy is required to remove a 2s-electron than a 2p-electron. Hence, Be has higher ionisation energy than B.