1. Honors Chemistry Chapters 3 & 4
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ATOMIC THEORY
Honors Chemistry
Chapters 3 & 4

2. Topics of Discussion Summarize the Development of Atomic Theory
Examine Atomic Structure

3. Laws Law of Conservation of Mass Law of Definite Proportions
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Laws
Law of Conservation of Mass
Law of Definite Proportions
Law of Multiple Proportions

4. Laws Law of Conservation of Mass Mass is neither Destroyed
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Laws
Law of Conservation of Mass
Mass is neither Destroyed
nor Created during ordinary
Chemical or Physical Reactions

5. Laws Law of Definite Proportions
A Chemical compound contains the same elements
in exactly the same proportions, by Mass,
regardless of size of sample or source of compound

6. Laws Law of Multiple Proportions
If 2 or more different compounds are composed of the Same 2 Elements,
then the ratio of the 2nd. element combined with the a certain mass of the 1st. element is always
a ratio of small whole numbers

7. Development of Atomic Theory
Democritus
Believed that matter was made up of atoms
Atoms were invisible particles
Atoms were indestructible particles
Lost out to Aristotle who stated that matter was continuous

8. Development of Atomic Theory
Dalton (1808)
Explains the Laws of conservation of mass, definite proportion and multiple proportion
Elements are composed of extremely small particles called atoms
Atoms of the same element are identical in size mass and properties. Atoms of different elements differ in size. Mass and properties

9. Development of Atomic Theory
Dalton (1808) cont.
Atoms cannot be subdivided, created, or destroyed.
Atoms of different elements combine in simple whole-number ratos to form chemical compounds
In chemical reactions , atoms are combined, separated or rearranged

10. Development of Atomic Theory
J.J. Thomson (1897)
Discovers the electron
(mass and a high charge)
Proposes the “Plum-Pudding“ model
Atom is neutral
Electrons embedded in a sphere of positive charge

11. Development of Atomic Theory
Rutherford (1911)
Gold foil experiment
Discovers that the atom has a nucleus
Extremely small
Extremely dense
Positive charge
Electrons move around the nucleus

12. Gold Foil Experiment

13. Development of Atomic Theory
Bohr (1913)
Electrons circle nucleus in specific circular paths at fixed distances from the nucleus
Each electron orbit has a Specific Energy or energy level
A Quantum of energy is required to move from one orbit to the next
Works for Hydrogen only!

14. Development of Atomic Theory
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Development of Atomic Theory
Millikan discovers electron charge and Mass of an electron (1909)
Chadwick discovers Neutron (1932)
De Broglie proposes particle wave behavior of Electron (1923)
Schrödinger writes an equation to determine probability of electron location

15. Development of Atomic Theory
Electron Cloud Model (present)
Based on Schrödinger's wave equation
Visual model of the probable locations of the electron in an atom

16. Development of Atomic Theory

17. Atomic Structure Properties of sub-atomic particles
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Atomic Structure
Properties of sub-atomic particles
(proton, neutron, & electron)
Charge
Location in Atom
Symbols
A(mass number) & Z (atomic number)
Proton Atomic Number = Z
Positive charge p+ , 11H
nucleus
accounts for atoms Mass
Neutron no charge n0, 10n
accounts for atoms mass
Electron negative charge e-, 0-1e
Cloud around the nucleus
mass but very small compared to proton or neutron
accounts for atom size
Nuclear forces hold nucleus together
Mass Number A= #protons +#neutrons
Atomic Number = Z = # protons
All atoms are electrically neutral = #electrons = #protons

18. Atomic Structure PROTON Location Center of atom; nucleus area Charge
Symbol
Center of atom; nucleus area
Positive p
ATOMIC NUMBER (Z) = number of protons in the atom

19. Atomic Structure Neutron To find the number of neutrons in an atom:
Location
Charge
Symbol
Center of atom; nucleus area
No charge (0) n
To find the number of neutrons in an atom:
Mass number of the element – number of protons (atomic number) = A (number of neutrons

20. In a neutral atom, # of electrons = # of protons
Atomic Structure
Electron
Location
Charge
Symbol
In shells around the nucleus of the atom.
Negative e
In a neutral atom, # of electrons = # of protons

21. Atomic Structure Element-A # p+ #n0 #e- Beryllium-9 Oxygen-16
Sulfur-32 4 5 4 8 8 8 16 16 16

22. Atomic Structure IONS Ions are charged particles.
Atoms gain or lose ELECTRONS are ions.
Lose e- --- more positive --- positive charge
Gain e- --- more negative ---negative charge
Na lose 1e- = Na1+ ( = 1+)

23. Atomic Structure
ION
# p+
#e-
Cl1-
Mg2+
Fe3+ 17 18 12 10 26 23

24. Atomic Structure Isotopes are: Naturally occur or man made
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Atomic Structure
Isotopes are:
Atoms of the same element
That have different masses
Naturally occur or man made
Nuclide general erm for any isotope of any element

25. Atomic Structure Practice: 1. Element D has 6 protons and 7 neutrons.
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Atomic Structure
Practice:
1. Element D has 6 protons and 7 neutrons.
Element F has 7 protons and 7 neutrons.
2. Element J has 27 protons and 32 neutrons.
Element L has 27 protons and 33 neutrons.
3. Element X has 17 protons and 18 neutrons.
Element Y has 18 protons and 17 neutrons.
4. Element Q has 56 protons and 81 neutrons.
Element R has 56 protons and 82 neutrons.

26. Atomic Mass Average Atomic Mass This is the mass on the Periodic Table
Weighted average
Of all naturally occurring isotopes
This is the mass on the Periodic Table
This is the mass we use for calculations
Can you calculate a weighted average?

27. Atomic Mass ISOTOPE % in Nature MASS Copper-63 69.17% 62.929599 amu
100.00%

28. Atomic Mass ISOTOPE % in Nature MASS Carbon-12 98.89% 12.000 amu
100.00%