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CGP EDU Academic Team
Published on: August 12, 2026
The correct order of first ionisation enthalpy of given elements is
A
B
C
D
Text Solution
Verified by ExpertsThe correct answer is:
A
: In general, along a period, the ionisation enthalpy increases with increase in atomic number and decrease in atomic size. Among the given elements of the second period, 
is smallest among the four. Hence, it has highest ionisation enthalpy. Electron in Be has to be removed from filled 
orbital which is more energy demanding than 
, in which electron has to be removed from 
orbital. Li has smallest ionisation enthalpy due to greater size.
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