Download Atomic Structure - Physical Science

Atomic Structure
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Democritus:
Dalton:
Thomson:
Rutherford:
Bohr:
400 BC
1803
1897
1911
1913
Vocabulary
• Atomic Number: Number of protons in an
atom of an element
• Mass Number: Number of protons and
neutrons in an atom
• Isotope: Elements have atoms with different
numbers of neutrons
• Atomic Mass: Weighted average of all the
isotopes of an element
Atomic Mass
• Multiply the mass number for each isotope by
its percentage abundance. Add all of the
answers. This gives you the weighted average
or atomic mass
• Element A has three isotopes with mass
numbers of 22, 23 and 25. The percentage of
these isotopes is 38, 53 and 9% respectively
• (22)(.38) + (23)(.53) + (25)(.09) = 22.8amu
Worksheet Answers
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1) (24)(.18) + (26)(.47) + (31)(.35) = 27.39
2) (15)(.07) + (21)(.22) + (24)(.71) = 22.71
3) (38)(.12) + (44)(.26) + (47)(.62) = 45.14
Cu: 1s22s22p63s23p64s23d9
Ag: 1s22s22p63s23p64s23d104p65s24d9
Cs: 1s22s22p63s23p64s23d104p65s24d105p66s1
I: 1s22s22p63s23p64s23d104p65s24d105p5
Democritus
• All matter is made up of individual particles
called atoms
• No experimental evidence
John Dalton
• All matter is made up of individual particles
called atoms
• Based on many experiments done by others
and his own experiments on gases and
chemical reactions
Dalton’s Theory
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All elements are composed of atoms
Atoms of the same element are all alike
Each elements atoms are unique
Compounds contain atoms of more than one
element
• Elements in a compound always combine in
the same proportion..
Thomson’s Experiment
• Cathode ray tube
• Tube Demo
Thomson’s Interpretation of His Results
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Cathode rays are negatively charged particles
These particles have a very small mass
All elements have these particles
Atoms are made of smaller parts
Thomson’s Atomic Model
• Chocolate chip ice cream model
• Chips are negative particles
• Ice cream is positive charge
Rutherford’s Experiment
Gold Foil
Alpha particle emitter
Detection Screen
Lead Box
• Designed to check Thomson’s atomic model
• Performed by graduate students Geiger and
Marsden
• Predict the results based on Thomson’s model
Geiger and Marsden’s Results
Expected
Actual
Rutherford’s Interpretations
• Result: Most of the particles went straight through
• Interpretation: Most of the atom is empty space
• Result: Some of the positive particles deflected
• Interpretation: Very small area is positively charged
• Result: A few of the particles bounced off
• Interpretation: Very small area is massive…
Rutherford’s Atomic Model
Rutherford’s Atomic Model
Bohr’s Atomic Model
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• Atomic collapse problem
Electrons can only be found in specific regions
around the nucleus called “orbitals”
Electrons can only have specific amounts of
energy called “energy levels”
Electrons can only emit or adsorb energy
when they change energy levels
NYC
Major Energy
Levels
Orbital Shapes & Number of
Energy Sublevels orbitals
Number of
electrons
Total
Electrons
1
s
1
2
2
2
3
s p
s p d
1 + 3
1 + 3 + 5
2 + 6
2 + 6 + 10
8
18
4
s p d f
1 + 3 + 5 + 7 2 + 6 + 10 + 14
32
5
s p d f g
1 + 3 + 5 + 7 2 + 6 + 10 + 14
32 +
6
s p d f g h
1 + 3 + 5 + 7 2 + 6 + 10 + 14
32 +
7
s p d f g h
1 + 3 + 5 + 7 2 + 6 + 10 + 14
32 +
The orbital shapes letters are
derived from the characteristics
of the orbitals spectroscopic
lines: sharp, principal, diffuse,
and fundamental, the rest are
named in alphabetical order
Major Energy Levels Overlap
1s
2s
3s
4s
5s
6s
7s
2p
3p
4p
5p
6p
7p
3d
4d
5d
6d
7d
4f
5f
6f
7f
Electron Configuration
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Lithium (Li)
Sodium (Na)
Oxygen (O)
Sulfur (S)
Potassium (K)
Strontium (Sr)
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1s22s1
1s22s22p63s1
1s22s22p4
1s22s22p63s23p4
1s22s22p63s23p64s1
1s22s22p63s23p64s23d104p65s2
For each of the above elements calculate the total
number of electrons in the highest major energy level.
Electron Configuration
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Lithium (Li)
Sodium (Na)
Oxygen (O)
Sulfur (S)
Potassium (K)
Strontium (Sr)
1s22s1
1s22s22p63s1
1s22s22p4
1s22s22p63s23p4
1s22s22p63s23p64s1
1s22s22p63s23p64s23d104p65s2
Valance Electrons
• The electrons in the highest major energy
level are known as the valance electrons.
These are the electrons that are involved
when an atom forms compounds. They
are responsible for the chemical and
physical properties of an element.