ionization potential

Ionization Potential Ionization Potential

1M.Qudratullah Saqib, Chem Engg.

By,Engr. Muhammad Qudratullah Saqib.UET Lahore.

ContentsContents Introduction to Ionization Energy Factors affecting the Ionization Energy Effective nuclear charge Atomic size i.e. atomic radius Principle quantum number Shielding effect Half filled and completely filled orbitals Nature of orbitals The extent of penetration of valence electrons

Trends in Ionization Potential

2M.Qudratullah Saqib, Chem Engg.

Ionization EnergyIonization Energy

The process of removing an electron from an isolated atom to form a positive ion.

First ionization energy (I1):

Amount of energy required to remove the most loosely bound electron from an isolated gaseous atom to form a cation.

Second ionization energy (I2):

Amount of energy required to remove a second electron from the gaseous monopositive cation to form di-positive cation.

3M.Qudratullah Saqib, Chem Engg.

Ionization energies are usually expressed in electron volts (eV) per atom or in kilo-Joules per mol (kJ/mol) --> 1eV/atom=96.48 kJ/mol

Value of each ionization energy will increase with each removed electron, since the attractive influence of the nucleus increases and will require more energy for the removal of an electron from more positive charges.

Ionization energies measure how tightly electrons are bound to atoms. Low energies indicate ease of removal of electrons and vice versa.

Ionization Energy(Cont.)Ionization Energy(Cont.)

4M.Qudratullah Saqib, Chem Engg.

Ionization Energy(Cont.)Ionization Energy(Cont.)

5M.Qudratullah Saqib, Chem Engg.

Factors affecting Ionization Factors affecting Ionization PotentialPotential Effective nuclear charge Atomic size i.e. atomic radius Principle quantum number Shielding effect Half filled and completely filled orbitals Nature of orbitals The extent of penetration of valence electrons

6M.Qudratullah Saqib, Chem Engg.

Factors affecting Ionization Factors affecting Ionization Potential(Cont.)Potential(Cont.)Effective Nuclear Charge:

Greater the magnitude of effective nuclear charge, higher is the amount of energy needed to remove the outermost shell

electron.

Atomic Size: Higher the value of atomic radius of an atom, lower will be

the ionization energy.

7M.Qudratullah Saqib, Chem Engg.

Factors affecting Ionization Factors affecting Ionization Potential(Cont.)Potential(Cont.)Principal Quantum Number (n):

With the increase of principal quantum number of the orbital from which the electron is to be removed, the

magnitude of ionization potential decreases.

Shielding Effect:With the increase of shielding effect ionization potential

decreases.

8M.Qudratullah Saqib, Chem Engg.

Factors affecting Ionization Factors affecting Ionization Potential(Cont.)Potential(Cont.)Half-filled and completely-filled orbitals:

The ionization potential of an atom having half-filled or completely-filled orbitals in its electronic configuration is

relatively higher than that expected normally from its position in the periodic table.

Nature of Orbitals:To remove an electron from f-orbital will be easiest while to

remove the same from s-orbital will be the most difficult according to following order,

ns < np < nd < nf

9M.Qudratullah Saqib, Chem Engg.

Ionization energy generally increases from left to right in a period because of the increase in nuclear charge and decrease in atomic radius.

Ionization energies generally decrease down a group due to the shielding effect and increase in atomic size.

Deviations from these trends can usually be traced to repulsion between electrons, particularly electrons occupying the same orbitals.

When all valence electrons have been removed, the ionization energy takes a quantum leap.

Trends in Ionization PotentialTrends in Ionization Potential

10M.Qudratullah Saqib, Chem Engg.

Trends in Ionization PotentialTrends in Ionization Potential

11M.Qudratullah Saqib, Chem Engg.

Trends in Ionization PotentialTrends in Ionization Potential

12M.Qudratullah Saqib, Chem Engg.