1. Chemistry Unit 3 Electrons in Atoms Chapter 5

2. 5.1 The Evolution of Atomic Models
The work of Dalton, Thomson and Rutherford began an age of exploration that culminated with a model of the atom that described a dense nucleus surrounded by electrons. This model continued to be modified as more data was collected.

3. Bohr model- Electrons are arranged in concentric circular paths (orbits) around the nucleus Called the planetary model Electrons have particular paths with fixed energy, which he called its energy level

4. Quantum mechanical model It comes from the mathematical solutions to the Schrodinger equation The probability of finding an electron within a certain volume of space surrounding the nucleus can be represented by a cloud (electron cloud) The cloud represents where the electron can be found approximately 90% of the time.
Sodium
atom

5. In Summary…

6. Energy level - region around the nucleus where the electron is likely to be moving. -An electron can jump from one level to another by absorbing energy.

7. Quantum - the amount of energy required to move an electron from its present energy level to the next higher energy level

8. Atomic orbital – the region in space where the electron is likely to be found
A quantum mechanical model of a hydrogen atom, which has one electron, in its state of lowest energy. The varying density of the spots indicates the relative likelihood of finding the electron in any particular region.

9. Electrons can be described by a series of 4 quantum numbers
Electrons can be described by a series of 4 quantum numbers. You must be familiar with these!

10. 1. Principle quantum number (n) -describes the principal energy level an electron occupies -values of 1,2,3,4,etc 1 2 3 4 5 6 7

11. Question
What energy level are the following elements in? Sr Pb

12. 2. Azimuthal quantum number (l) -describes the shape of atomic orbitals -s orbitals are spherical, p orbitals are peanut shaped, d orbitals are daisies and f orbitals are fancy -designates a sublevel -values of 0 up to and including n-1 0=s, 1=p, 2=d, 3=f

13. s orbital
Spheres

14. p orbitals
Peanuts

15. d orbitals
Daisies or Doughnuts

16. Fancy
f orbitals

17. Where do I find the orbital shapes?

18. 3) Magnetic Quantum Number
We therefore need a third quantum number, known as the magnetic quantum number (m), to describe the orientation in space of a particular orbital.

19. 4) Spin Quantum number
Each of these orbitals can accommodate up to two electrons (with opposite spins), forming the basis of the periodic table.

20. Movie: periodic table of the elements: t10-20ml ms 1
0(s) 3d
ENERGY 4s 2
0(s) 3p
1(p)
-1, 0, 1 3s 3
0(s) 2p
1(p)
-1, 0, 1 2s
2(d)
-2,
-1, 0, 1, 2 1s 4
0(s)
Movie: periodic table of the elements: t10-20

21. Question:
What would the quantum numbers be for the outer electron of a chlorine atom?

22. Quick and Easy Electron Configuration
First, number the periods 1-7, 3-6 and 4-5 as shown by your teacher. 1 2 3 4 5 6 7 S 3 4 5 6 P D 45 F