JEE Main20262 April 2026Morning ShiftChemistryClassification of Elements and Periodicity in PropertiesActual
Given below are two statements : Statement (I) : The first ionisation enthalpy of the elements Na, Mg, Cl and Ar follows the order Na > Mg > Cl > Ar. Statement (II) : Among Ca, Al, Fe and B, the third ionisation enthalpy is very high for Ca. In the light of the above statements, choose the correct answer from the options given below :
Options
- ABoth Statement I and Statement II are true
- BBoth Statement I and Statement II are false
- CStatement I is true but Statement II is false
- DStatement I is false but Statement II is true
Correct answer
D. Statement I is false but Statement II is true
Step-by-step solution
The first ionisation enthalpy generally increases across a period from left to right due to an increase in effective nuclear charge. For the third period elements Na , Mg , Cl , and Ar , the correct order of first ionisation enthalpy is Ar > Cl > Mg > Na . Thus, Statement I is false. The electronic configuration of Ca is [ Ar ] 4s^2 . After the removal of two electrons, Ca ²⁺ attains the highly stable noble gas configuration of Argon [ Ar ] . Removing a third electron requires breaking this stable noble gas core, w