1. Bohr – Rutherford Atomic Model:
Bohr & Rutherford combined their theories to create the current simplified atomic model
The atom is made up of three sub-atomic particles:
Protons
Electrons
Neutrons

2. The Atom: - + Proton Electron Neutron 1 amu nucleus outside nucleus
Sub-Atomic Particle
Charge
Mass
Location +
1 amu
nucleus
Proton
outside nucleus -
negligible
Electron
Neutron
none
1 amu
nucleus

3. The Atom: electron neutron nucleus proton
education.jlab.org/ qa/atom_model.html

4. Nucleus: Electrons: Contains protons & neutrons
Overall positive charge (+)
Contains nearly all mass (dense)
Electrons:
Located outside nucleus
Easily moved, lost or gained
Negative charge (-)

5. The Atom – Important Info:
Since atoms are neutral,
the number of protons (+)
equals the number of electrons (-)
Every atom has a symbol & two numbers associated with it.
Ex.
Atomic Number C 12 6
The number of protons
The smaller number
Mass Number
The mass of an atom
The number of protons & neutrons
The bigger number

6. O Ex #1 For the following atom, state the… 8 16 i) mass number
ii) atomic number
iii) # of protons
iv) # of electrons
v) # of neutrons 16 O 16 8 8 8 8
16 – 8 = 8

7. Na Ex #2 For the following atom, state the… 11 23 i) mass number
ii) atomic number
iii) # of protons
iv) # of electrons
v) # of neutrons 23 11 11 Na 11 23 11
23 – 11 = 12

8. Ar Ex #3 For the following atom, state the… 18 40 i) mass number
ii) atomic number
iii) # of protons
iv) # of electrons
v) # of neutrons 40 18 18 Ar 18 40 18
40 – 18 = 22

9. Cu Ex #4 For the following atom, state the… 29 64 i) mass number
ii) atomic number
iii) # of protons
iv) # of electrons
v) # of neutrons 64 29 29 Cu 29 64 29
64 – 29 = 35

10. P Ex #5 For the following atom, which statement is TRUE? 15 31
A) The atomic number is 31.
B) The atom has 15 neutrons.
C) The atom has 16 electrons.
D) The atom has 15 protons & 15 electrons. P 31

11. Ex #6 Given a neutral atom, which statement is TRUE?
A) An atom always has the same number of electrons as neutrons.
B) Electrons & neutrons are found in the nucleus.
C) The atomic number states the number of neutrons.
D) An atom always has the same number of electrons as neutrons.

12. Key Points to Remember
An atom’s atomic number is equal to the number of protons (smaller number)
An atom is neutral, therefore the number of protons & electrons are equal
An atom’s mass number is equal to the protons & neutrons together (bigger number)

13. Key Points to Remember Atoms are made up of:
Protons
Electrons
Neutrons
Protons & Neutrons are located in the nucleus
Electrons are located outside the nucleus

14. Electrons:
Recall, in the Bohr-Rutherford atomic model, electrons are located outside the nucleus
Electrons are organized into:
Electron shells or
Energy levels or
Orbitals
Be familiar with
all the terms,
especially the
first two

15. Electrons:
*Simplified –
3rd shell holds 18 electrons
4th shell holds 32 electrons
Each electron shell differs in size & the number of electrons it can hold (capacity)
Shows maximum #
of electrons in
each shell
Electron Shell
Capacity
1st
2 electrons
2nd
8 electrons
3rd
8 electrons*
4th
2 electrons*
Shells can be partially
filled or empty

16. Bohr – Rutherford Diagram:
Is a picture of an atom, showing its protons, electrons & neutrons.
Ex. Li 7 3
Protons = 3
First
Electrons= 3
Neutrons= 4
Second
3 P+
4 N0
2 e-
1 e-
Third

17. F Ex #1 First Second Third 9 19 Draw a Bohr-Rutherford diagram for:
Protons = 9
Electrons= 9
Neutrons= 10
9 P+
Second
Third
10 N0
2 e-
7 e-

18. B Ex #2 First Second Third 5 11 Draw a Bohr-Rutherford diagram for:
Protons = 5
Electrons= 5
Neutrons= 6
5 P+
Second
Third
6 N0
2 e-
3 e-

19. Mg Ex #3 12 24 Draw a Bohr-Rutherford diagram for: Protons = 12
Electrons= 12
Neutrons= 12
12 P+
12 N0
2 e-
8 e-
2 e-

20. K Ex #4 19 39 Draw a Bohr-Rutherford diagram for: Protons = 19
Electrons= 19
Neutrons= 20
19 P+
20 N0
2 e-
8 e-
8 e-
1 e-

21. Ex #5
Which of the following diagrams best represents the Bohr-Rutherford model of… Be 9 4 A) C)
4 P+
4 P+
3 e-
2 e-
2 e-
5 N0
5 N0
2 e- B)
5 P+
2 e-
2 e-
4 N0

22. Ex #6
Draw a Bohr-Rutherford diagram for each of the following atoms: P 31 15 N 14 7 Al 27 13
8 e-
7 P+
8 e-
15 P+
5 e-
13 P+
7 N0
16 N0
5 e-
2 e-
14 N0
2 e-
2 e-
3 e-

23. Find the number of Protons, Electrons & Neutrons
Key Points to Remember
Electrons are located outside the nucleus in electron shells
In the…
1st shell – 2 electrons
2nd shell – 8 electrons
3rd shell – 8 electrons*
4th shell – 2 electrons*
In Bohr-Rutherford diagrams:
Place Protons & Neutrons in nucleus
Place Electrons in appropriate shells
First
Find the number of Protons, Electrons & Neutrons