Bohr – Rutherford Atomic Model
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Bohr – Rutherford Atomic Model
Neils Bohr improved Rutherford’s model by placing electrons in distinct energy levels or “shells” rather than an electron “cloud”
Bohr & Rutherford combined their theories to create the current simplified atomic model
The atom is made up of three sub-atomic particles:
ProtonsElectronsNeutrons
Bohr – Rutherford Atomic Model:
The Atom:Sub-Atomic
ParticleCharge Mass Location
Proton
Electron
Neutron
+
-none
1 amu
negligible
1 amu
nucleus
outside nucleus
nucleus
education.jlab.org/ qa/atom_model.html
The Atom:
nucleus
electron neutron
proton
Nucleus: Contains protons & neutrons Overall positive charge (+) Contains nearly all mass (dense)
Electrons: Located outside
nucleus Easily moved, lost or
gained Negative charge (-)
Every atom has a symbol & two numbers associated with it.
Ex.
The Atom – Important Info:
C 12
6
Mass Number
Atomic Number
•The mass of an atom
•The bigger number•The number of protons & neutrons
•The number of protons•The smaller number
Since atoms are neutral, the number of protons (+)
equals the number of electrons (-)
For the following atom, state the…i) mass numberii) atomic numberiii) # of protonsiv) # of electronsv) # of neutrons
O 16
816
8
8
8
16 – 8 = 8
For the following atom, state the…i) mass numberii) atomic numberiii) # of protonsiv) # of electronsv) # of neutrons
Na23
1123
11
11
11
23 – 11 = 12
For the following atom, state the…i) mass numberii) atomic numberiii) # of protonsiv) # of electronsv) # of neutrons
Ar40
1840
18
18
18
40 – 18 = 22
Cu64
2964
29
29
29
64 – 29 = 35
For the following atom, state the…i) mass numberii) atomic numberiii) # of protonsiv) # of electronsv) # of neutrons
For the following atom, which statement is TRUE?
P 3115
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.
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 has the same number of electrons as protons.
Atoms are made up of: Protons Electrons Neutrons
Protons & Neutrons are located in the nucleus
Electrons are located outside the nucleus
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)
Activities: Physical Science Worksheet #7
Once you’ve completed the
worksheet, continue with the rest of the
lesson
Recall, in the Bohr-Rutherford atomic model, electrons are located outside the nucleus
Electrons are organized into:Electron shells or Energy levels orOrbitals
Electrons:
Be familiar with all the terms, especially the
first two
Each electron shell differs in size & the number of electrons it can hold (capacity)
Electrons:
Electron Shell
Capacity
1st 2 electrons
2nd 8 electrons
3rd 8 electrons*
4th 2 electrons*
Shows maximum # of electrons in
each shell
Shells can be partially filled or empty
*Simplified – 3rd shell holds 18 electrons4th shell holds 32 electrons
Is a picture of an atom, showing its protons, electrons & neutrons.
Ex.
Bohr – Rutherford Diagram:
Protons =
Electrons=
Neutrons=
334
3 P+
4 N0 2 e- 1 e-
Li73
Draw a Bohr-Rutherford diagram for:
Protons =
Electrons=
Neutrons=
9910
9 P+
10 N0 2 e- 7 e-
F199
Draw a Bohr-Rutherford diagram for:
Protons =
Electrons=
Neutrons=
556
5 P+
6 N0 2 e- 3 e-
B115
Draw a Bohr-Rutherford diagram for:
Protons =
Electrons=
Neutrons=
121212
12 P+
12 N0 2 e- 8 e-
Mg2412
2 e-
Draw a Bohr-Rutherford diagram for:
Protons =
Electrons=
Neutrons=
191920
19 P+
20 N0 2 e- 8 e-
K 3919
8 e- 1 e-
Be 9 4
Which of the following diagrams best represents the Bohr-Rutherford model of…
A)
4 P+
5 N0 2 e-3 e-
B)5 P+
4 N0 2 e- 2 e-
C)4 P+
5 N0 2 e- 2 e-
Draw a Bohr-Rutherford diagram for each of the following atoms:
P 3115
N 147
Al 2713
15 P+
16 N02 e-
8 e-5 e-
7 P+
7 N0 2 e-5 e- 13 P+
14 N02 e-
8 e-
3 e-
The Neutron
The Rutherford-Bohr model of the atom did not answer the question:
“What holds the nucleus together given that it is made up of entirely of positive protons?”
The Neutron
In 1932, James Chadwick discovered that a third sub-atomic particle called the neutron holds the protons in the nucleus together.
Neutrons are located in the nucleus and have no charge…they are neutral.
Nucleus: Contains protons & neutrons Overall positive charge (+) Contains nearly all mass (dense)
Electrons: Located outside
nucleus Easily moved, lost or
gained Negative charge (-)
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
Find the number of Protons,
Electrons & Neutrons
Activities: Physical Science Worksheet #8
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