Assertion (A) The `alpha`-hydrogen atom in carbonyl compounds is less acidic.
Reason (R) The anion formed after the loss of `alpha`-hydrogen atom is resonance stabilised.

Explanation

To analyze the assertion and reason provided in the question, we will break down the concepts of acidity in carbonyl compounds and the stability of the anion formed after the loss of alpha-hydrogen.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that the alpha-hydrogen atom in carbonyl compounds is less acidic.
- In carbonyl compounds (like aldehydes and ketones), the alpha-hydrogen is attached to the carbon adjacent to the carbonyl group (C=O).

2. **Understanding the Reason (R)**:
- The reason states that the anion formed after the loss of the alpha-hydrogen atom is resonance stabilized.
- When an alpha-hydrogen is removed (deprotonation), it forms an enolate ion, which is resonance-stabilized.

3. **Analyzing the Acidity of Alpha-Hydrogens**:
- The acidity of a hydrogen atom is determined by the stability of the resulting anion after deprotonation.
- In carbonyl compounds, when the alpha-hydrogen is removed, the resulting enolate ion can be represented by multiple resonance structures.

4. **Resonance Stabilization**:
- The enolate ion can be depicted as having a negative charge on the oxygen atom and can also have a double bond between the carbon and the carbonyl carbon.
- This delocalization of the negative charge across different atoms (through resonance) increases the stability of the anion.

5. **Conclusion**:
- Since the anion formed after the loss of alpha-hydrogen is resonance stabilized, the alpha-hydrogens in carbonyl compounds are actually more acidic than what the assertion claims.
- Therefore, the assertion (A) is **false** while the reason (R) is **true**.

### Final Answer:
- Assertion (A) is false, and Reason (R) is true.