Ionization energy



Ionization energy

(or potential) of an element is defined as “The amount of energy required or needed to remove an electron from the neutral gaseous atom to form unipositive ion , for example Na → Na+ + e + energy

This is measured in electron volts per atom or kJ mol-1. For example IE of Na is 495 kJ mol-1.

Trends in ionization energy of elements.

1 – Ionization energy increases from left to right in a period. This is because the nuclear charge increases and the electrons are more strongly held and hence more energy is required to remove an electron.

2 –  Ionization energy decreases down a group. This is because as we go down a group, the outermost electron (which is being removed) is farther from the nucleus and hence less energy is required to remove it.



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