1. Quantum Model of the Atom

2. Scientists had discovered that light could behave both as a particle and as a wave
French scientist Louis de Broglie suggested that electrons also had a dual wave-particle nature
Electrons could be considered to be waves confined to a space around the nucleus
The waves had to be certain frequencies, and thus had a certain amount of energy

3. A German physicist, Werner Heisenberg, explained that it is impossible to pinpoint a location for an electron in an atom
Electrons are detected by their interaction with photons
Photons have about the same amount of energy as electrons, so when a photon interacts with an electron, it knocks the electron off course

4. Heisenberg Uncertainty Principle
It is impossible to determine simultaneously both the position and velocity of an electron or any other particle.

5. Austrian physicist Erwin Schrödinger developed a mathematical equation that treated electrons as waves.
Only waves of specific energies, and therefore frequencies, provided solutions to the equation. These solutions were called wave functions.
This confirmed Bohr’s theory of quantifiable energy levels for electrons in an atom

6. Schrödinger’s wave equation along with the Heisenberg Uncertainty Principle laid the foundation for modern quantum theory.
Quantum theory is a mathematical description of wave properties of electrons and other very small particles.

7. They exist in 3-D regions called orbitals
The wave functions resulting from Schrödinger’s Wave Equation give only the PROBABILITY of finding an electron at a given place around the nucleus.
Therefore electrons don’t travel around the nucleus in orbits as in Bohr’s model
They exist in 3-D regions called orbitals
Orbitals come in different shapes and sizes
The orbitals are actually electron clouds, or probable locations for electrons

8. Quantum numbers are used to describe the properties of atomic orbitals and the properties of electrons in those orbitals
It takes 4 quantum numbers to describe the total energy state of each electron in an atom
The first 3 quantum numbers indicate the main energy level, the shape, and the orientation of the orbital
The 4th quantum number describes the spin state of the electron occupying the orbital

9. Principal Quantum Number
Symbol is n
Indicates the main energy level occupied by the electron
Lowest energy level is 1
As n increases, the distance from the nucleus increases
More than one electron can be in the same main energy level
Sometimes main energy levels are called shells.

10. Angular Momentum Quantum Number
Symbol is l
Indicates the shape of the orbital
At each main energy level there are n possible shapes
At the first level there is 1 shape
At the second level there are 2 shapes
At the 3rd level there are 3 shapes
At the 4th level there are 4 shapes

11. The shapes or orbitals are assigned letters
s orbitals are spherical
p orbitals are dumb-bell shaped
d orbitals are more complex
f orbitals are even more complex

13. Every atomic orbital is designated by both its principal quantum number and the letter representing its shape
1s orbital is the s-shaped orbital in the first main energy level
2s orbital is the s-shaped orbital in the second main energy level

14. Magnetic Quantum Number
Symbol is m
Indicates the orientation of the orbital around the nucleus
s orbitals are spherical so they can only be oriented 1 way
p orbitals can be oriented three ways
Along the x-axis, the y-axis, and the z-axis

16. d orbitals can be oriented in 5 ways

19. f orbitals can be oriented in 7 ways

21. The total number of orbitals in a main energy level is n2
At the first energy level there is 1 orbital: 1s
At the second energy level there are 4 orbitals: 2s, and three 2p orbitals
At the third energy level there are 9 orbitals: 3s, three 3p orbitals, and five 3d orbitals
At the fourth energy level there are 16 orbitals:
4s, three 4p orbitals, five 4d orbitals, and 7 4f orbitals.

22. Spin Quantum Number
An electron in an orbital behaves like a planet spinning on its axis
The electron exists in one of two spin states
The spin quantum number indicates which of the two spin states the electron has.
One orbital can only hold 2 electrons and they have opposite spin states.

23. Since each main energy level contains n2 orbitals, and each orbital can hold 2 electrons, then the number of electrons that can “fit” in each energy level is 2n2
The first energy level has 1 orbital and can hold 2 electrons
The second energy level has 4 orbitals and can hold 8 electrons