1. The Bohr Model & Bright-Line Spectra
Take notes on what is written in blue…

2. The Bohr Model & Bright-Line Spectra
How does Bohr’s atomic theory explain the unique bright-line spectra of the elements?
The farther an electron is from the nucleus, the more energy that electron will have.
1st shell
2nd shell
3rd shell
low energy
Nucleus +
higher energy
Empty space
even higher
energy

3. The Bohr Model & Bright-Line Spectra
Recall that a H-1 atom has one proton and no neutrons.
Recall that a H-1 atom has one electron in the 1st shell when in the ground state.
1st shell
2nd shell
3rd shell
low energy
Nucleus e- 1p 0n +
higher energy
Empty space
even higher
energy

4. The Bohr Model & Bright-Line Spectra
If a H-1 atom were to absorb a precise amount of energy, its electron could jump up to a higher energy electron shell.
The electron is now said to be in an excited state.
1st shell
2nd shell
3rd shell e-
low energy
Nucleus e- 1p 0n
higher energy
Empty space
even higher
energy

5. The Bohr Model & Bright-Line Spectra (Write this down…)
Electrons are in the excited state when they in a shell that is higher than their ground state.
Electrons can only jump up to an excited state by absorbing a precise amount of energy.
All electrons in the excited state will return to their ground state.
Electrons can NEVER jump to a shell that is lower than their ground state.

6. The Bohr Model & Bright-Line Spectra
The excited electron can release all of its absorbed energy and jump back to its proper place in the atom – the 1st shell.
The electron has now returned to its ground state.
1st shell
2nd shell
3rd shell e-
low energy
Nucleus e- 1p 0n
higher energy
Empty space
even higher
energy

7. The Bohr Model & Bright-Line Spectra
An excited electron can release part of its absorbed energy and jump back toward its proper place in the atom.
The electron is still in an excited state.
1st shell
2nd shell
3rd shell e-
low energy
Nucleus e- 1p 0n
higher energy
Empty space
even higher
energy

8. The Bohr Model & Bright-Line Spectra
Whether an excited electron releases some or all of its absorbed energy, the emitted energy is always released as a photon – a packet of light energy.
1st shell
2nd shell
3rd shell e-
low energy
Nucleus e- 1p 0n
higher energy
Empty space
even higher
energy

9. The Bohr Model & Bright-Line Spectra
The larger the jump back is, the higher energy the released photon will be.
When an electron jumps back to the 1st shell in a hydrogen atom, the released photon will be in the ultraviolet region of the light spectrum.
When an electron jumps back to the 2nd shell in a hydrogen atom, the released photon will be in the visible region of the light spectrum.
When an electron jumps back to the 3rd shell in a hydrogen atom, the released photon will be in the infrared region of the light spectrum.

10. The Bohr Model & Bright-Line Spectra
The four lines of the visible bright-line spectrum for a sample of hydrogen are produced by the following electron jumps.
An electron
jumping from
the 5th shell to
the 2nd shell
An electron
jumping from
the 3rd shell to
the 2nd shell
An electron
jumping from
the 6th shell to
the 2nd shell
An electron
jumping from
the 4th shell to
the 2nd shell
hydrogen
400 nm
500 nm
700 nm

11. The Bohr Model & Bright-Line Spectra
Bohr’s atomic theory also includes an advanced mathematical equation that predicts the energy of each released photon with the energy jumps of the electrons!
Unfortunately, Bohr’s equation can only exactly predict the energy for the released photons of hydrogen!
ΔE = x10-18
[ ]
ni2
nf2 1

12. The Bohr Model & Bright-Line Spectra
Even though Bohr’s atomic model has some serious flaws, it is still used to explain many chemical phenomena.
Ex.1) Which electron shell has the most energy?
(1) 1st shell (3) 3rd shell
(2) 2nd shell (4) 4th shell
Ex.2) An electron becomes excited by
(1) absorbing energy (3) producing energy
(2) releasing energy (4) destroying energy

13. The Bohr Model & Bright-Line Spectra
Ex.5) In order for an excited state electron to return to the ground state it must
(1) absorb energy (3) store energy
(2) release energy (4) destroy energy
Ex.6) A line in an element’s bright-line spectrum is produced when
(1) a ground state electron absorbs energy
(2) an excited state electron releases energy
(3) an excited state electron absorbs energy
(4) a ground state electron releases energy

14. The Bohr Model & Bright-Line Spectra
Ex.7) Which of the following types of light has the most energy?
(1) radio waves (3) visible light
(2) infrared light (4) ultraviolet light
Ex.8) Which of the following colors in the visible spectrum has the most energy?
(1) red (3) yellow
(2) violet (4) blue R O Y G B V

15. The Bohr Model & Bright-Line Spectra
Ex.9) A bundle of light energy is called a(n)
(1) photon (3) wave
(2) electron (4) quark
Ex.10) In order for a ground state electron to jump up to a higher shell and become an excited state electron, it must
(1) absorb an inexact amount energy
(2) release an inexact amount energy
(3) absorb a precise amount of energy
(4) release a precise amount of energy

16. Assignment
SA 5.3 page 146 #16-21