Question

Why is the ionisation enthalpy of boron less than beryllium?

Answer 1

the value of ionization enthalpy of elements increase as we go across the group because as the atomic number increases the elements require more energy to gain electron

Answer 2

Answer:

(1) The electronic configuration of boron (B, Z =5) is 1s², 2s², 2p¹ and that of beryllium (Be, Z = 4) is 1s², 2s²

(2) Due to paired electrons in 2s-orbital, Be acquires extra stability but boron has only one unpaired electron in p-orbital.

(3) Thus less energy is required to remove a p-electron than a paired s-electron in the same principal shell. Therefore, ionisation enthalpy of boron is less than beryllium