The amount of energy needed to be supplied to an isolated atom in its gaseous and ground state to remove its most loosely bound electron to infinity is called ionization potential. Higher the value of Ionization Potential (IP), the more difficult it is to ionize the atom. Its SI unit is Joule (J). The commonly used unit of ionization potential per mole is KiloJoule per mole (KJmol-1).
Variation of Ionization Potential in a period
Value of IP increases from left to right in a period in the Modern Periodic Table. It is because of the following reasons:
- Decreasing atomic radius
- Increase nuclear charge
Variation of Ionization Potential in a group
Value of IP decreases from top to bottom in a group in the Modern Periodic Table. It is because of the following reasons:
- Increasing atomic radius
- Dominance of addition of shell over increase in nuclear charge
Exception in variation of Ionization Potential
- Value of IP for noble gas elements is the highest in a period
- Value of IP for alkali metals is the lowest in a period
- Value of IP for half-filled or full-filled ultimate orbitals of elements is more than its preceding element
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