Question

although Boron is smaller in size as compared to beryllium enthalpy of beryllium is higher than Boron

Answer 1

come on Be is smaller than B

Answer 2

Boron Electronic configuration = 1s² 2s² 2p¹

Beryllium Electronic Configuration = 1s² 2s²

According to the periodic properties in ionisation enthalpy, going across a period gives increased ionisation energy.

That is if we move across a period, ionisation enthalpy increases. So Boron must b have higher ionisation enthalpy than beryllium. But in the case of boron, the electron present in ' p ' orbital is guarded by the 2 s orbital electrons. Hence less energy is required for removing them.

Since s orbital electrons have higher affinity than p orbital electrons towards nuclear attraction, Boron's valence electron can be easily taken than that of Beryllium. Hence Boron has less ionisation enthalpy than Beryllium.