1. Arrangement of Electrons in Atoms
Chapter 5
Arrangement of Electrons in Atoms

2. Light
Dual Nature of Light: Light can act like waves, and as straight line particles.
Light is one type of _____________ ____________which is a form of Energy that has wavelike behavior
Other types of em radiation are: x-rays, uv, infrared, microwaves & radio, and together they all form the _____________________________
(look at p.92 Figure 4-1 on next slide)

4. The Wave
The speed of all em waves through a vacuum (space) and through air is:
_______________________________
The length of each individual wave is known as it’s __________________ () which is the length between corresponding points on adjacent waves, usually measured in ____________ (1nm = 10-9m)
The ______________ (f or ) is how many waves pass a particular point in a second and is measured in waves/second = _________ (Hz)

5. The relationship between them is as follows:
c = f x 
E.g.
What is the wavelength & color of light that has a frequency of 6 x 1014 Hz (1/s)?
f =
c = =

6. If em radiation is directed towards a piece of metal, it may have enough energy to knock out electrons. This is known as the ________________________.
A German physicist: Max Planck, explained the reason why, but first let’s look at what he discovered.

7. When an object gets hot, it emits energy in small specific amounts called quanta.
A quantum is the minimum amount of energy that can be lost or gained by an atom.
The frequency determines the Energy by:
________
Where Planck’s constant = h = ______________
E.g. What is the Energy of Green light with a frequency of 6 x 1014 Hz ? f=
E = h.f

8. It was Einstein that proposed that light
It was Einstein that proposed that light acted like a stream of particles called photons.
A ___________ is a particle of em radiation that has zero mass and carrying a _______ of energy
There must be a minimum amount of energy to eject electrons from a metal
__________, Planck realized that the em radiation providing the energy, must be of a certain frequency.
Different metals need different minimum amounts of energy, and therefore frequencies

9. The Hydrogen Atom
Consider the H atom with its one electron spinning around its one proton.
When the electron is closest to the proton/nucleus which is at its lowest energy state, the atom is in its ground state.
When energy, like heat, is supplied to the atom, the electron jumps to a higher orbit which is at a higher energy state. The atom is now in an excited state.

10. When the electron ______________________________________________or a lower energy state, it emits a photon of radiation with a specific amount of energy, and not continuous amounts of energy.
Therefore, specific ______________ of light are emitted when excited Hydrogen “cools” down.

11. Bohr Model
Niels Bohr (Danish) proposed a model that stated: “the e- of a H atom can circle the nucleus in allowed paths called __________”
Between the orbit and the nucleus, is a large empty space where the e- ___________ exist

12. Convert circular orbits to lines
When the ____ atom gets excited, the e- jumps to another specific orbit and not somewhere in between – like going up a ladder
When the e- falls back, it ______ ______ in the form of a photon (a bundle of light energy)
Convert circular orbits to lines

13. The amount of Energy is _______ to the difference in the two _________ (orbit) levels
So there are specific frequencies (colors of light) given off when the H e- ______ from the higher orbits giving its visible line spectrum

14. Quantum Model of Atom
Question is: Why can’t e-’s be in an orbit between the ________ Energy levels?
French scientist Louis DeBroglie pointed out that the electron orbits acted like the behavior of waves.
i.e. you can only have a certain amount of waves in a given _________________ – not ½ of a wave
If you can only have specific # of waves, then based on the formula _______ you can only have specific f’s, which in turn translates into specific Energy levels.

15. Heisenberg Uncertainty Principle
States that: “it is impossible to determine _____________ the position and velocity of an electron or any other particle”
This is because whatever you use to observe subatomic particles, will affect the particles themselves.
i.e you can’t observe/measure without disturbing it.

16. Quantum Numbers
____________________(n) indicates the main energy level (or shell) occupied by the electron.
Principle _____________________ is also referred to as the Principle Energy Level (n).
n = 1,2,3,4… where n = 1 is the closest to the nucleus.
(Diagram: H atom Circular orbits to linear 1,2,3,…)

17. The electron now has an __________ number of Energy levels (shells) to jump to depending on the Energy input.

18. Each Energy level (n) divides up further into sublevels/subshells.
How many divisions depends on the original Energy level.
The 1st E level has 1 sublevel (s only)
2nd 2 sublevels (s and p)
3rd 3 sublevels (s, p, and d)
4th 4 sublevels (s, p, d and f)
: :
i.e nth n sublevels.

19. s-Orbital
Each sublevel is assigned an ___________ __________ _________ ( l ) and has a particular shape. The first sublevel in each E level has a spherical shape. (assigned the letter s). There is only 1 possible orientation. (aka orbital)
The shape is determined by the electron’s path over time.

20. p- Orbital
The ________ ________in each E level has a figure eight shape. (assigned the letter p ). There are 3 possible orientations (orbitals)

21. d- orbital
The _______ _______in each E level is designated an has a four leaf clover shape. (assigned the letter d ). There are 5 possible orientations (orbitals)

23. f, g and h are indescribable!
The _______ ________in each E level has an indescribable shape. (assigned the letter ___ ). There are 7 possible orientations (orbitals)
The ________ _________in each E level has an indescribable shape. (assigned the letter ___ ). There are 9 possible orientations (orbitals).
The _______ ________in each E level has an indescribable shape. (assigned the letter ____ ). There are 11 possible orientations (orbitals).
Summary on board

24. To sum up:
Principle E level # sublevels sublevels
(n) (n) s
s 2p
s 3p 3d
s 4p 4d 4f
s 5p 5d 5f 5g
s 6p 6d 6f 6g 6h
We expect the order of the orbitals to increase as follows:
1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 5g 6s 6p …

25. But in reality, from Energy level 3, there are some overlaps.
There is an easy way to determine the actual order.
( demonstrate diagonal method)
So, the actual order is as follows:
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 8s

26. Now each _______ (orientation) can hold 2 ________.
The s sublevel which has 1 orbital can hold 2 e- ’s p d f g h

27. So now, the BIG picture is as follows:
Principle # # of each Total Total
E level sublevels type of # of # of
orbital orbitals e- ‘s
(n) (n) s p d f g h (n2) (2n2 )

28. Electron Configuration
Each orbital (orientation) can hold _____and can be represented by a box, circle or underline. (diagram) (complete orbital chart)
For each electron, they orbit with a spin around in 2 different ways – ________________________.
One type of spin produces a magnetic field with a North up (_________), and the other produces a North down (__________) (diagram)
The electrons are represented by _______ pointing up or down, depending on their spin. (diagram)

29. e.g. Hydrogen has 1 e- that occupies the lowest Energy level – 1s. 
According to the:
Pauli Exclusion principle, in order for 2 electrons to occupy the same orbital, they must have opposite spins.
e.g. Hydrogen has 1 e- that occupies the lowest Energy level – 1s.  1s
Helium has 2 e-’s that also occupies the lowest Energy level – 1s. 
Opposing arrows that represent opposite spins.

30. Rules of Procedure for Electron Configuration:
___________: an electron occupies the lowest energy orbital that can receive it.
(i.e. start from the bottom)
____________________: no 2 electrons in the same atom can have the same set of 4 quantum numbers.
(i.e. no more than 2 electrons per orbital)
________________: orbitals of equal energy are each occupied by one electron before any orbital is occupied by a 2nd electron, and all electrons in singly occupied orbitals must have the same spin.
(i.e. don’t double up until each orbital has an up arrow)

31. Now do Oxygen & explain:

32. _______________________: the way electrons are arranged amongst the orbitals.
A special notation is used which consists of:
the principle E level, the sublevel & the # of electrons in that sublevel.
e.g. the 1 electron in Hydrogen occupies the 1st orbital, in the 1st sublevel, in the 1st E level. (diagram)
e.g. the 2 electrons in Helium also occupy the 1st orbital, in the 1st sublevel, in the 1st E level. (diagram)
e.g. for Lithium, which has 3 electrons, it’s as follows:
(diagram)