Which of the following is not the basic postulates of Dalton's atomic theory ?

Options

A. Each element is composed of extremely small particles called atoms
B. Atoms are neither created nor destroyed in a chemical reaction.
C. Atoms of all elements are alike, including their masses.
D. None of these

Answer

To determine which of the following statements is not a basic postulate of Dalton's atomic theory, we will analyze each statement based on the principles of the theory.

### Step-by-Step Solution:

1. **Understanding Dalton's Atomic Theory**:
- Dalton's atomic theory consists of several postulates that describe the nature of matter and its composition. The key points include:
- Matter is made up of indivisible particles called atoms.
- Atoms of the same element are identical in mass and properties.
- Atoms of different elements have different masses and properties.
- Atoms combine in whole number ratios to form compounds.
- Atoms can combine in different ratios to form different compounds.
- Atoms cannot be created or destroyed in a chemical reaction.

2. **Analyzing the Statements**:
- **Statement 1**: "Each element is composed of extremely small particles called atoms."
- This statement is correct and aligns with Dalton's postulate that matter is made of atoms.

- **Statement 2**: "Atoms can neither be created nor destroyed in a chemical reaction."
- This statement is also correct and reflects Dalton's postulate regarding the conservation of atoms in reactions.

- **Statement 3**: "Atoms of all elements are alike including their masses."
- This statement is incorrect. Dalton's theory states that atoms of the same element are identical, but atoms of different elements are not alike and have different masses.

3. **Conclusion**:
- Based on the analysis, the statement that is not a basic postulate of Dalton's atomic theory is **"Atoms of all elements are alike including their masses."** This is option number three.

### Final Answer:
The statement that is not a basic postulate of Dalton's atomic theory is option number three: **"Atoms of all elements are alike including their masses."**

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