1. Ch. 4.2 Quantum Model of the Atom
Atomic Structure

2. POINT > Recall Bohr’s atomic model
POINT > Identify electrons as wave-like particles
POINT > Define Heisenberg’s uncertainty principle
POINT > Describe electron orbitals as three dimensional probabilities
POINT > Describe how quantum numbers define electron orbitals

3. POINT > Recall Bohr’s atomic model
Problem:
Bohr’s model worked for
hydrogen, but was inaccurate
with atoms having more than one electron
Bohr

4. POINT > Identify electrons as wave-like particles
Light has wave-like properties
Louis de Broglie showed that electrons also have wave-like properties
de Broglie showed that electrons undergo diffraction and interference like waves (see p 98-99)

5. POINT > Describe Heisenberg’s uncertainty principle
Heisenberg’s uncertainty principle: It is impossible to know the position and velocity of an electron
Any attempt to locate an electron alters its path
This is true for any atomic particle or photon

6. WB CHECK:
What did de Broglie discover about electrons?
electrons only exist at discrete energy levels
the location and velocity of electrons is uncertain
electrons undergo diffraction and interference
electrons have a much smaller mass than protons

7. WB CHECK:
What did Heisenberg tell us about electrons?
electrons only exist at discrete energy levels
the location and velocity of electrons is uncertain
electrons undergo diffraction and interference
electrons have a much smaller mass than protons

8. Erwin Shrödinger used mathematical models to describe electron motion
POINT > Describe electron orbitals as three dimensional probabilities
Erwin Shrödinger used mathematical models to describe electron motion
Electrons are restricted to certain energy levels (supported Bohr)
Electrons do not follow specific paths (unlike Bohr model)

9. POINT > Describe electron orbitals as three dimensional probabilities
Shrödinger’s equations were the foundation of quantum theory The location of an electron is described as a mathematical probability in space The result is the electron cloud model of the atom

10. Electron cloud model of the atom
POINT > Describe electron orbitals as three dimensional probabilities
Electron cloud model of the atom
Where the cloud is more dense, there is a higher probability of finding an electron (Usually drawn where electrons are ~90% of time)

11. Shrodinger’s equations
WB CHECK:
Shrodinger’s equations
supported Bohr’s idea that electrons have discrete energy levels
supported Bohr’s idea that electrons move on specific paths
described electron orbitals as mathematical probabilities
a and b
a and c
b and c

12. Models through Time…
Quantum Mechanical
(Electron Cloud Model)

13. Describes energy levels an electron can have
POINT > Describe electron orbitals as three dimensional probabilities
The quantum model:
Describes energy levels an electron can have
Describes an atomic orbital as a region of space with a high probability of finding an electron

14. POINT > Describe electron orbitals as three dimensional probabilities

15. Homework:
Read pages
Pre-read pages
Atomic Spectra Lab Due Friday