1. The Atom as we know it (via the Atomic Theory)
And so…
How do we teach others the arrangement of the subatomic particles?

2. The Atomic Theory all matter is made of atoms
explains what atoms look like, and how and why they behave the way they do
see past notes for previous atomic theories (Dalton, Thomson, Rutherford)

3. Atomic Regions and Parts
(e-) Electrons (Electron Cloud):
each has a (-1) charge
little to no mass
located outside of the nucleus
Nucleus
dense, (+) mass in the atom’s center
(p+) protons
each has a (+1) charge
has a mass of 1 a.m.u.
(atomic mass unit)
(n) neutrons
no charge
But this image doesn’t do enough to explain exactly where the electrons are or what the electrons are doing. How can we give more clarification about the electrons?

4. The Bohr Model of the Atom
The Electron Cloud:
the region of the atom where electrons are located
occupies most of the atom’s volume (space)
divided into energy levels (see picture below)
Nucleus
First Energy Level:
Can hold 2 e-
Second Energy Level:
Can hold 8 e-
Third Energy Level:
Can hold 18 e-
Fourth Energy Level:
Can hold 32 e-

5. **New Terms** Valence Electrons Energy Levels
The following terms are used to describe characteristics or locations of electrons
Valence Electrons
e- in the outermost energy level
could be in any energy level
determine chemical properties
 Energy Levels
The “rings” indicating how the “distance” and electron is from the nucleus
e- can move from one energy level to the next by absorbing or releasing energy
ex: excited electrons absorb energy and move to higher energy levels

6. Wow – there’s a lot of information here!
Neils Bohr discovered the energy levels in the electron cloud
Electrons could jump energy levels
Looked like the solar system
So far the Periodic Table gives us the following information about an element:
# of Protons from the atomic number
# of total e- also from the atomic number (in neutral atom)
# of energy levels from the Period (row #)
# of valence e- from the Group (column #)
And the # of Neutrons can be calculated once we know the mass #
# N = mass # - atomic #

7. Let’s try a Bohr model of Potassium (K-41)
____ N
___ e-
___ e- e- e-
___ e- e-
There will be 19 electrons total
Atomic number is 19 2 8
P=19
N= 22 8 1
This is the where the valence electrons go
Let’s try a Bohr model of Potassium (K-41)
1) Draw the Nucleus and enter:
A. # P (= Atomic #)
B. #N (= mass # - #P)
2) Determine the Total # e- (= #P)
3) Determine the # of energy levels and draw them (= Period or row#)
4) Enter the # of valence e- in the last energy level (= Group or column#)
5) Fill in the inside energy levels with electrons, starting at the first and working out, ending with the second to last energy level using up the remaining e-.
Remember:
1st energy level holds up to 2 e-
2nd energy level holds up to 8 e-
3rd energy level holds up to 18 e-
4th energy level holds up to 32 e-
Potassium is in group 1A = 1 valence electron

8. This has been an example of a Bohr model using a NEUTRAL atom
the smallest piece of an element in which there is no charge
an atom with the same number of protons and electrons
# protons = # electrons
How many protons?
How many neutrons? 12 C 6
How many electrons? 6 6p 6n
How many energy levels? 2 4 2
How many on the last (2nd ) energy level?
How many on the first energy level?