Back to Topic 5.1 — Structure of the atom
5.1.6Physics12 flashcards

Bohr model and quantized energy levels (HL)

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5.1.6
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Bohr energy levels of hydrogen?

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All 12 Flashcards — Bohr model and quantized energy levels (HL)

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Card 1formula

Question

Bohr energy levels of hydrogen?

Answer

$E_n = -\dfrac{13.6}{n^2}$ eV, with n = 1, 2, 3, … The levels are **discrete** (quantized).

Card 2concept

Question

Why are the Bohr energy levels negative?

Answer

The zero is set at the just-free electron (n → ∞), so any **bound** electron has **less** energy — hence negative.

Card 3definition

Question

What is the ground state of hydrogen?

Answer

n = 1, with $E_1 = -13.6$ eV — the **lowest** (most tightly bound) level.

Card 4example

Question

Energy of the n = 2 level of hydrogen?

Answer

$E_2 = -13.6/4 = -3.40$ eV.

Card 5formula

Question

Photon energy when an electron changes level?

Answer

$hf = E_i - E_f$ — the photon energy equals the size of the energy drop.

Card 6comparison

Question

Emission vs absorption of a photon?

Answer

**Emission**: electron jumps **down**, atom gives out a photon. **Absorption**: electron jumps **up**, atom takes a photon in.

Card 7concept

Question

Why does hydrogen give a line spectrum?

Answer

Its levels are **discrete**, so only certain energy drops — and hence certain photon energies — are possible.

Card 8definition

Question

Ionisation energy of hydrogen?

Answer

**13.6 eV** — the energy to lift the electron from the ground state (−13.6 eV) up to 0 eV (free).

Card 9example

Question

Photon energy for n = 3 → 2 in hydrogen?

Answer

$(-1.51) - (-3.40) = 1.89$ eV $= 3.0\times10^{-19}$ J.

Card 10process

Question

Convert an energy from eV to joules?

Answer

Multiply by $1.60\times10^{-19}$ (1 eV = 1.60×10⁻¹⁹ J).

Card 11concept

Question

Which transition gives the highest-frequency photon?

Answer

The one with the **largest** energy drop — falling down to n = 1.

Card 12concept

Question

How do the levels change as n rises?

Answer

The gaps **shrink** (1/n²), so the levels **crowd together** approaching 0 eV.

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