ionisation enthalpy & variation with group & periods

Ionisation enthalpy(energy):

Ionisation enthalpy may ne defined as amount of energy required to remove most loosely bound electron from an isolated gaseous atom to from gaseous cation.

eg.

solid→liquid→gas→M(g) -1e^- →M(g) ^+
heat not require gas atom gaseous cation

Variation of ionisation energy in a group:

Ionisation energy decrease from top to button ina group because size of the atom increase. attraction between nucleus and valence electron decrease.

Variation of ionisation energy in a period:

Ionisation energy increase from left to right in a period because as effective nuclear charge increase .attractive between nucleus and valence electron increase so Ionisation energy is increase in period.

Successive ionisation energy:

After the removable of first electron it is possible to remove 2nd, 3rd, and even more electron .Amout of energy required to remove successive or subsequent electron are known as successive ionisation energy.

I. E(3) >I.E(2) >I.E(1)
Amount of energy required to remove 1st electron called I. E(1) and
Amount of energy required to remove 2nd electron called I. E(2) and

Amount of energy required to remove 3rd electron called I. E(3) .
It is observed that

I. E(3) > I. E(2) > I. E(1)

second ionisation energy is more than first ionisation energy. because after the removable of first electron the atom change into mono valent cation n+1 in effective nuclear charge is more. so more energy is required to remove 2 nd electron. hence I. E (2) is more than I. E(1).

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