Li (520), Be (899) and C (1086) kJ "mol"^(-1) ionisation enthalpy then B contain which are ionisation enthalpy 800 or 900 kJ/mol why ?

Li (520), Be (899) and C (1086) kJ "mol"^(-1) ionisation enthalpy then

1.	Li (520), Be (899) and C (1086) kJ "mol"^(-1) ionisation enthalpy then B contain which are ionisation enthalpy 800 or 900 kJ/mol why ?
Answer» Solution :`800 KJ" mol"^(-1)` because order of IONISATION ENTHALPY in second period is `Li lt B lt Be lt C`.