JEE Main202311 Apr 2023Morning ShiftChemistryClassification of Elements and Periodicity in PropertiesActual
For elements B , C , N Li , Be , O and F , the correct order of first ionisation enthalpy is
Options
- ALi   <   Be   <   B   <   C   <   O   <  
- BB   <   Li   <   Be   <   C   <   N   <  
- CLi   <   Be   <   B   <   C   <   N   <  
- DLi   <   B   <   Be   <   C   <   O   <  
Correct answer
D. Li   <   B   <   Be   <   C   <   O   <  
Step-by-step solution
The first ionisation energy varies predictably across the periodic table. As we move from left to right across a period, the ionisation energy of elements increases. This is due to the decrease in the size of atoms across a period. The valence electrons get closer to the nucleus of an atom as we move from left to right due to increased nuclear charge. The force of attraction between the nucleus and the electrons increases and hence more energy is required to remove an electron from the valence shell. Ionisation ene