1. Orbits and Line Spectra
The Bohr Model:
Orbits and Line Spectra

2. C12-2-04 ENERGY AND ATOMIC MODELS
OUTCOME QUESTION(S):
C ENERGY AND ATOMIC MODELS
Explain average atomic mass using isotopes and their relative abundance.
Include: radioisotopes
Describe the electromagnetic spectrum in terms of frequency, wavelength, and energy.
Include: Plank’s Equation, quantum, photon
Understand the historical development of the Quantum Mechanical Model of the atom.
Describe how unique line spectra are created for each element.
Include: Bohr model
Vocabulary & Concepts 
Ground State Absorption Spectra

3. How do scientists explain the very predictable, replicable structure of line spectra with the disorganized Rutherford model?

4. Bohr Model (1913) – proposed that spectral lines are light from excited electrons.
Restricted electrons to fixed orbits (n) of different quantized energy levels
Created an equation for energy of an electron at each orbit
ΔE = x J Z2
nf2
ni2 _
His created equations correctly predicted the structured spectral lines of Hydrogen…

5. Electron fall to ground state
Electrons absorb energy and jump from ground state (its resting state) to a higher unstable energy level (excited state).
Electron fall to ground state
– releasing a photon of energy equivalent to
the distance moved.
“unstable” is the KEY - electrons are attracted to the nucleus and can’t stay away for long
Free Atom e−
EMR
Ground State
Excited State
Ionization
Absorption
nucleus
> Threshold Energy
< Threshold Energy

6. ΔE = E higher-energy orbit - E lower-energy orbit
= Ephoton emitted
= hf
The difference in energy requirements between orbits determines the “colour” of photon released by the electron when it drops back towards the nucleus

7. 3. Levels are discrete (like quanta) – No in-between
4. Every jump/drop has a specific energy
requirement - same transition, same photon.

8. _ ΔE = -2.18 x 10-18 J Z2 nf2 ni2 = Ephoton emitted = hf
Predicts the type of EMR released for any transition
ΔE = Enf - Eni
= Ephoton emitted
= hf
Change in energy is released as a photon of EMR

9. What is the energy of the photons released when an electron drops from n=5 to n=2 in a hydrogen atom?
ΔE = x J Z2
nf2
ni2 _
ΔE = x J 12
2f2
5i2 _
ΔE = x J 1 4 25 _
ΔE = x J

10. Visible light – blue to be exact
What type of energy is released when an electron drops from n=5 to n=2 in a hydrogen atom?
ΔE = x J
c = λƒ λ
6.91 x 1014 Hz
= x 108 m/s
E = hf ƒ
6.626 x J·s
= x J λ
= x 10-7 m λ
= 434 nm ƒ
= x 1014 Hz
Visible light – blue to be exact

11. The size of the nucleus will affect electron position around the atom – and the energy requirements
Each element has a unique line spectrum as each element has a unique atomic configuration – making it jump/drop unique
17 p+

12. We only “see” the emitted energy of an transitioning electron if it is a photon of energy in our visible spectrum – some emissions lines are invisible to us

13. Notice energy absorbed is the same as energy released
Absorption spectrum – portion of visible light absorbed by an element – heating up.
Emission spectrum – portion of visible light emitted by that element – cooling down.

14. C12-2-04 ENERGY AND ATOMIC MODELS
CAN YOU / HAVE YOU?
C ENERGY AND ATOMIC MODELS
Explain average atomic mass using isotopes and their relative abundance.
Include: radioisotopes
Describe the electromagnetic spectrum in terms of frequency, wavelength, and energy.
Include: Plank’s Equation, quantum, photon
Understand the historical development of the Quantum Mechanical Model of the atom.
Describe how unique line spectra are created for each element.
Include: Bohr model
Vocabulary & Concepts 
Ground State Absorption Spectra