Which one of the following statements is incorrect in relation to ionisation enthalpy?

Options

A. Ionization enthalpy increases for each successive electron.
B. The greatest increase in ionization enthalpy is experienced on removal of electron from core of noble gas configuration.
C. End of valence electrons is marked by a big jump in ionization enthalpy.
D. Removal of electron from orbitals bearing lower `n` value is easier than from orbitals having higher `n` value.

Explanation

To solve the question regarding which statement is incorrect in relation to ionisation enthalpy, we will analyze the properties of ionisation enthalpy and the factors that influence it.

### Step-by-Step Solution:

1. **Understanding Ionisation Enthalpy**:
Ionisation enthalpy (or ionisation energy) is the energy required to remove an electron from an atom or ion in its gaseous state. It is a measure of how strongly an atom holds onto its electrons.

**Hint**: Remember that ionisation enthalpy is influenced by the atomic structure and the effective nuclear charge.

2. **Factors Affecting Ionisation Enthalpy**:
- **Atomic Size**: As atomic size increases, ionisation enthalpy generally decreases because the outermost electrons are farther from the nucleus and experience less attraction.
- **Effective Nuclear Charge**: As the effective nuclear charge increases, ionisation enthalpy increases because the electrons are held more tightly by the nucleus.
- **Electron Shielding**: The presence of inner electrons can shield the outer electrons from the full effect of the nuclear charge, affecting ionisation enthalpy.

**Hint**: Consider how atomic size and nuclear charge interact to influence ionisation energy.

3. **Analyzing the Statements**:
- Check each statement provided in the options to see if they align with the principles of ionisation enthalpy.
- Look for statements that contradict the established trends (e.g., if a statement suggests that ionisation enthalpy increases with increasing atomic size).

**Hint**: Compare each statement against the principles discussed to identify any contradictions.

4. **Identifying the Incorrect Statement**:
- After evaluating the statements, identify the one that does not conform to the trends of ionisation enthalpy. This could be a statement that incorrectly suggests a relationship between atomic size and ionisation enthalpy or misrepresents the effect of nuclear charge.

**Hint**: Focus on the relationship between atomic size and ionisation energy, as this is a common area of confusion.

5. **Conclusion**:
- Once the incorrect statement is identified, conclude your answer by clearly stating which option is incorrect and providing a brief justification based on the principles of ionisation enthalpy.

**Hint**: Summarize your findings to reinforce your understanding of the topic.

### Final Answer:
The incorrect statement in relation to ionisation enthalpy is the one that contradicts the established trends, such as suggesting that ionisation enthalpy increases with increasing atomic size or that effective nuclear charge has no effect on ionisation enthalpy.