- Exam
- JEE Main
- Year
- 2024
- Date
- 29 January
- Shift
- Morning Shift
- Subject
- Chemistry
- Chapter
- Classification of Elements and Periodicity in Properties
JEE Main 2024 · 29 January · Morning Shift · Chemistry · Classification of Elements and Periodicity in Properties
Given below are two statements : one is labelled as Assertion A and...
Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R:
Assertion A: The first ionisation enthalpy decreases across a period.
Reason R: The increasing nuclear charge outweighs the shielding across the period.
In the light of the above statements, choose the most appropriate from the options given below:
Options
- ABoth A and R are true and R is the correct explanation of A
- BA is true but R is false
- CA is false but R is true
- DBoth A and R are true but R is NOT the correct explanation of A
Correct answer
C. A is false but R is true
Step-by-step solution
Ionization enthalpy is defined as the minimum amount of energy that is required to remove the most loosely bounded electron that is the electron present in the outermost shell, from an isolated gaseous atom.
First, ionisation energy increases along the period because effective nuclear charge increases. Along the period increases which outweighs the shielding effect.
Hence, option C is the answer.