Why Atoms Emit Light Bohr Model Concept

❓ Concept Question

What are the main postulates of Bohr’s Atomic Model?

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🖼 Concept Image

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✍️ Short Concept

This concept is based on:

👉 Bohr atomic model
👉 Quantization of angular momentum
👉 Electronic transitions.

Main idea:

Electrons revolve only in certain allowed orbits without losing energy.

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🔷 Step 1 — Stationary Orbits 💯

According to Bohr:

Electrons revolve around nucleus in fixed circular orbits.

These are called:

$$\text{Stationary orbits}$$

In these orbits:

$$\boxed{ \text{No energy is radiated} }$$

So electron remains stable.

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🔷 Step 2 — Quantization of Angular Momentum

Bohr proposed:

$$mvr=\frac{nh}{2\pi}$$

Where:

• $m$ = mass of electron
• $v$ = velocity
• $r$ = orbit radius
• $n$ = orbit number

$$n=1,2,3,\dots$$

This means angular momentum is quantized.

Only specific orbits are allowed.

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🔷 Step 3 — Energy Absorption and Emission

Electron absorbs or emits energy only during transition between orbits.

Energy relation:

$$\Delta E=E_2-E_1=h\nu$$

Where:

• $h$ = Planck constant
• $\nu$ = frequency of radiation

If electron jumps upward:

👉 Energy absorbed

If electron jumps downward:

👉 Energy emitted

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🔷 Step 4 — Energy of Orbit

For hydrogen atom:

$$E_n\propto-\frac1{n^2}$$

So:

✔ Smaller orbit → more negative energy

✔ Larger orbit → less negative energy

As:

$$n\to\infty$$

energy approaches zero.

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🔷 Step 5 — Spectral Lines Concept 🚨

Spectral lines are produced because of:

$$\boxed{ \text{Electronic transitions} }$$

Different transitions give different frequencies.

This explains hydrogen spectrum.

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🔷 Step 6 — JEE Trap Alert 🚨

❌ Electron continuously energy lose karta hai assume kar lena

❌ Angular momentum formula bhool jaana

❌ Orbit energy positive maan lena

Remember:

$$\boxed{ mvr=\frac{nh}{2\pi} }$$

and

$$\boxed{ E_n\propto-\frac1{n^2} }$$

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✅ Final Takeaway

Bohr model explains:

✔ Stability of atom

✔ Quantized orbits

✔ Hydrogen spectrum

using:

$$\boxed{ \Delta E=h\nu }$$

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⭐ Golden JEE Insight

For hydrogen-like atoms:

✔ Radius increases with:

$$n^2$$

✔ Energy becomes less negative as:

$$n$$

increases.

So higher orbit means:

👉 Higher energy
👉 Larger radius

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📚 Related Topics

• Faraday Law and Nernst Equation Combined Concept
• First Order Growth and Second Order Decay Trick
• Bond Pair and Lone Pair Counting Shortcut