1. Development of Atomic Models
Electrons in Atoms
Development of Atomic Models
Jot down 3 things you already know about atoms

2. Things Rutherford’s Atomic Model Could Explain
Protons and Neutrons composed the atomic nucleus
Electrons move around the nucleus in the same way that planets revolve around the sun

3. And Things it Couldn’t The chemical properties of elements:
Why do metals give off specific colors when heated?
He needed to better describe the behavior of electrons!

4. Rutherford’s Model Changed!
1913 – The Bohr Model
Energy of an atom changes when it absorbs or emits light
Electrons are only found in specific circular paths, or orbits around the nucleus
Each possible orbit have fixed energy levels

5. Can an electron move into different energy levels?
To move from one energy level to another, they need to gain or lose the right amount of energy
A quantum of energy is the amount of energy required to move an electron from on energy level to another
The amount of energy gained or lost is not always the same

6. Another Atomic Model is Developed
1926Schrodinger (Used Mathematical Solutions)
Quantum Mechanical Model – determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus

7. Where can you find electrons?
Atomic Orbitals – region in space in which there is a high probability of finding an electron
Principle energy levels (n = 1)
Energy sublevels (1)
Draw orbitals. Table on page 131.

8. Maximum numbers of electrons
Energy level n
# of electrons 1 2 8 3 18 4 32

9. Sublevels
Sublevel corresponds to a different shaped orbital

10. Change Proceeds to Lowest Energy
In an atom, electrons make the most stable arrangement
Electron Configuration- the ways in which electrons are arranged in various orbitals around the nucleus of an atom
Pencil demo

11. Aufbau Principle
Electrons occupy the lowest energy orbital first

12. Pauli Exclusion Principle
An atomic orbital may describe at most 2 electrons

13. Hund’s Rule
Electrons occupy orbitals of the same energy in a way that makes the number of electrons with the same spin direction as large as possible
Give examples. Then BATTTTLEEEEEEESHIPPPPPPPPPPPPP maybe next class

14. Energy Levels, Sublevels and Orbitals
A sublevel is a region IN the energy level
4 possible sublevels
Orbital is a region in the sublevel. Each orbital can hold only 2 electrons S
1 orbital
2 electrons p
3 orbitals
6 electrons d
5 orbitals
10 electrons f
7 orbitals
14 electrons

15. What is light?
Newton believed it was made up of particles BUT it was proven to consist of waves.
Wave cycles start at zero, increase to the highest value, passes through zero to reach its lowest value, and returns to zero again.

16. 3 Properties of Waves
Amplitude – the wave’s height from zero to the crest (highest point of the wave)
Wavelength – distance between the crests
Frequency – the number of wave cycles to pass a given point per unit of time

17. Calculate Wavelength λ= c/ν λ= Wavelength (m)
C= Speed of Light (2.998 x108 m/s)
ν= Frequency (/s)

18. Electromagnetic Spectrum

19. Practice!
Calculate the wavelength of the yellow light emitted by a sodium lamp. The frequency of the radiation is 5.10x1014 /s. What is the frequency of radiation with a wavelength of 5.00x10-8m?
x x1015/s

20. Atomic Spectra
When atoms absorb energy, electrons move into higher energy levels.
These electrons move into higher energy levels and lose energy by emitting light and returning to the lower energy levels.
The light emitted varies like a fingerprint

21. Electron Energy Ground State – Lowest possible energy of an electron
When an electron absorbs energy it enters an excited state
N= 2,3,4,5,6 etc.
A quantum of energy in the form of light is emitted when an electron drops to a lower energy level
Electronic Transition

22. Quantum Mechanics
Einstein proposed that light could be described as quanta of energy
Light quanta are known as particles

23. Classical vs. Quantum Classical Mechanics Quantum Mechanics
Describes the motions of bodies much larger than atoms
Quantum Mechanics
Describes the motions of subatomic particles and atoms as waves

24. Heisenberg Uncertainty Principle
It is impossible to know exactly both the velocity and position of a particle at the same time