Understanding Electron Orbitals and the Heisenberg Uncertainty Principle

1. Unit 3-2 Electron orbitals

2. The Heisenberg Uncertainty Principle If electrons are both particles and waves, then where are they in the atom? To answer this question, it is important to consider a proposal first made in 1927 by the German theoretical physicist Werner Heisenberg

3. The Heisenberg Uncertainty Principle • Heisenberg uncertainty principlestates that it is impossible to determine simultaneously both the position and velocity (speed)/momentum of an electron or any other particle • We can only predict the possibility of electron’s position at a certain time.

4. Schrodinger Wave Equation- no need to remember! • The square of the wave equation, 2, gives a probability density map of where an electron has a certain statistical likelihood of being at any given instant in time. • It is known as quantum mechanics.

5. The Quantum Numbers • Solving the wave equation gives a set of orbitals, and their corresponding energies. • An orbital is described by a set of 4 quantum numbers. • You don’t need to remember the quantum numbers except for n. • The principal quantum number, n: describes the energy level (shell) on which the orbital resides. • Azimuthal Quantum Number, l : defines the shape of the orbital. • Magnetic Quantum Number, ml : Describes the three-dimensional orientation of the orbital • Spin Quantum Number, ms : describes the spin of a electron in the orbital.

6. Principal Quantum Number, n • The principal quantum number, n, describes the energy level (shell) on which the orbital resides. it denotes the probable distance of the electron from the nucleus. • The values of n are integers ≥ 1.

7. Azimuthal Quantum Number, l • l defines the shape of the orbital. The same shaped orbitals in each shell are grouped into the sublevel/subshell. • There are only n subshells in the shell/energy level n. • For example, on 1st shell (n=1), there is only one kind of subshell which is s subshell : 1s • How many subshells does the 2nd shell contain? Silly professor dance funny

8. Magnetic Quantum Number, ml • Describes the three-dimensional orientation of the orbital. • Therefore, on any given energy level, there can be up to one s orbital, three porbitals, five dorbitals, seven forbitals, etc.

9. Spin Quantum Number, ms • Ms describes the behavior (direction of spin) of an electron within a magnetic field. • Therefore, each orbital can only hold up to 2 electrons. • s = 1 x 2e- = 2e- • p= 3 x 2e- = 6e- • d = 5 x 2e- = 10e- • f = 7x 2e- = 14e-

10. To sum up • Orbitals with the same value of n form a shell. • Different orbital types, within a shell, are grouped into subshells.

11. ssubshell • Only one orbital in each s subshell. • Spherical in shape. • Radius of sphere increases with increasing value of n.

12. Proton Neutron Electron S orbital(2 electrons maximum)

13. psubshell • Each orbital in p has two lobes with a node between them. • It has 3 orbitals(3 possible positions in the 3D space)

14. Proton Neutron Electron P orbital (6 electrons max.)

15. dSubshell • Four of the five orbitals have 4 lobes; the other resembles a p orbital with a doughnut around the center. • 5 possible positions of a orbital of the 3D space = 5 orbitals

16. fsubshell Tro, Chemistry: A Molecular Approach

17. Energy Levels, Orbitals, Electrons

18. Energy Shells and Subshells Tro, Chemistry: A Molecular Approach

19. Why are Atoms Spherical? Tro, Chemistry: A Molecular Approach

20. Homework • Page 315 question 55, 56, 60