The ionization energy of
an element is the minimum energy required to remove the outermost electron from
its isolated gaseous atom in its ground state to form a positive ion.
First, second & third I.E.
value increases in the following order.
First I.E. < Second
I.E. < Third I.E.
Trends In Periodic Table
In A Group
I.E. decreases down the group due to
increases in no. of shells. Moreover Atomic radius & Shielding effect of
inner electrons also increases. Hence I.E. decreases. Thus it is easier to
remove electron from Cs than Li atom.
Along Period
I.E. increases along the period from
left to right.
It is because, along
the period positive charge on the nucleus increases due to increase in atomic
number but no. of shells remains same.
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