Which of the following is not a correct statement according to Rutherford's atomic model? — Atomic Structure Chemistry Question

💡 Solution & Explanation

### Step 1 - Key Postulates of Rutherford's Nuclear Model Rutherford's 1911 model postulated: 1. The nucleus is extremely small, dense, and positively charged. 2. Virtually **all the mass** of the atom is concentrated in the nucleus. 3. Most of the space inside an atom is empty. 4. Electrons revolve around the nucleus in circular orbits. ### Step 2 - Why "99%" is Incorrect The mass of an electron ($m_e \approx 9.1 \times 10^{-31}$ kg) is about $\frac{1}{1836}$ that of a proton. Even for heavy atoms, all electrons combined constitute less than $0.05\%$ of total atomic mass. Therefore: $$\text{Mass in nucleus} > 99.9\%$$ Stating exactly "99%" understates the true figure significantly — the correct statement should be "more than 99.9%". ### Step 3 - Evaluation of Options * **Option (A) 99% of mass centred in nucleus:** Incorrect statement — understates the actual value (>99.9%). This is the answer. * **Option (B) Most of atom is empty:** Correct statement — consistent with Rutherford. * **Option (C) Nucleus very small compared to atom:** Correct — $r_{\text{nucleus}} \approx 10^{-15}$ m vs $r_{\text{atom}} \approx 10^{-10}$ m. * **Option (D) Electrons revolve around nucleus:** Correct — Rutherford's postulate. $$\text{Correct Option (NOT correct): } \boxed{\text{A}}$$