Question

assertion - the first ionisation enthalpy of boron is lower than that of beryllium .
reason - atomic radius boron smaller than that of beryllium




a and r are true , r us crct expl of assertion .
a is true r is false .
r is true a is false

a and r are crct , r is not crct expl of assrertion
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Answer 1

Answer:

A is true and R is false.

Ionisation energy (I.E) of Beryllium is more than Boron .

Electronic configuration of Be: 1s2 2s2

Electronic configuration of B: 1s2 2s2 2p1

Beryllium stable fully filled configuration, therefore more amount of energy is required to remove an electron from Beryllium , whereas less amount of energy is required to remove an electron from valence p-orbital in Boron .

Hence Assertion is correct.

Across period atomic size decreases so the reason is incorrect.