Review:
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theory vs law
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the atomic theory
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contributions of early scientists
Oct 7­11:27 AM
The Atom
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the smallest particle of an element into which it can be subdivided
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an atom consists of a nucleus which contains protons and neutrons, as well there are electrons which orbit the atom ­
the nucleus is so tiny it would take 10,000 of them to stretch across the atom
(the nucleus is like a grain of sand on a football field which represents the atom)
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the nucleus is always positive because of protons
Oct 7­11:28 AM
1
Structure of an Atom
Oct 7­11:33 AM
Protons, Neutrons and Electons
Particle Relative Charge
Mass
Location in Atom
Heavy Positive
(similar to neutrons)
Inside the nucleus
Proton
Electron Light
Negative Orbiting the nucleus
Neutral Inside the Neutron Heavy (similar to nucleus
protons)
Oct 7­11:36 AM
2
Element
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a pure substance that cannot be broken down into smaller components
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all elements use symbols consisting of one or two letters (first letter is capitalized , second is not)
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all elements are listed on the Periodic Table of Elements (see page 50)
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this table was started by Dmitri Mendeleev who first sorted the elements by properties until he found a pattern (see page 48)
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Mendeleev also realized that there were some elements that may have existed but were not yet discovered. That is why the table will often have gaps to show elements that should be there
Oct 7­1:42 PM
Oct 7­1:53 PM
3
­
students will be required to know the chemical symbols for the following elements
1. Hydrogen
2. Sodium
3. Potassium
4. Magnesium
5. Calcium
6. Iron
7. Nickel
8. Copper
9. Zinc
10. Carbon
11. Nitrogen
12. Oxygen
13. Neon
14. Helium
15. Chlorine
16. Silicon
17. Silver
18. Gold
19. Mercury
20. Lead
Oct 7­1:55 PM
Oct 7­2:11 PM
4
Atomic Number
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equals the number of protons on a nucleus
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always a whole number, usually the top number in a Periodic Table
Atomic Mass
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the average mass of the atoms of an element
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written as a decimal number, usually below the element symbol
Oct 7­2:17 PM
Example
14
Atomic Number
Si
Element Symbol
Element Name
Silicon
Atomic Mass
28.1
Oct 7­2:19 PM
5
Determining protons, neutrons and electrons
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the protons of an element are the same as its atomic number
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the electrons equal the number of protons
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the neutrons are equal to atomic mass subtract atomic number (round down the atomic mass)
Oct 7­2:24 PM
Example:
Determine the protons, neutrons and electrons in the following
Element:
Symbol:
P
E
N
Copper
Sodium
Oxygen
Chlorine
Oct 7­2:27 PM
6
The Element Song
Readings:
Pages 38 ­ 49
Questions:
Page 47, #'s 1,2,6
Page 49, complete table in 2­2A
Activities:
Element Crossword and Wordsearch
Oct 7­2:43 PM
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