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Physical Science Chapter 4
Atomic Structure
Democritus and Aristotle◦ Democritus thought all matter consisted of
extremely tiny particles that could not be divided. (Cut aluminum foil in half)
◦ Also thought matter in liquids was round and smooth; in solids rough and prickly
◦ Aristotle thought there was no limit to the number of times matter could be divided.
4.1 Studying Atoms
Developed a theory to explain why the elements in a compound always behave in the same way.
Main Points◦ 1) All elements are composed of atoms.◦ 2) All atoms of the same element have the same
mass, and atoms of different elements have different masses.
◦ 3) Compounds contain atoms of more than one element.
◦ 4) In a compound, atoms of different elements always combine in the same way.
Dalton’s Atomic Theory
Used a cathode ray tube to show evidence for subatomic, charged particles.
Thomson’s Model
Plum pudding model (chocolate chip ice cream.
Negatively charged particles evenly spaced throughout a solid mass of positive charge.
Thomson continued
The Gold Foil Experiment – Evidence for a nucleus.
Rutherford’s Atomic Theory
Chapter 4Lesson 2
“Structure of the Atom”
A. An atom1. smallest part of matter2. Ripping paper example
B. Areas of an atom1. Nucleus – center of an atom
-holds protons and neutronsa. Protons (P) – positively charged
particle found in the nucleus.-has a mass of 1-has a charge of 1+
I. Subatomic Particles
b. Neutrons (N) – non-charged particle found in the nucleus.
-has a mass of 1-has no charge “0”
2. Electron Cloud – area around the nucleus which contains electrons
a. Electrons (e) – negatively charged particle found outside of the nucleus
-has a mass of 0-has a charge of 1--moves around the outside of the nucleus
Protons ElectronsNeutrons
Particle Mass Charge Location of particle
Particles in an Atom Review
Proton
Neutron
Electron
1
1
0
1+
0
1-
nucleus
nucleus
Electron cloud
A. Def – the # of protons in an atom’s nucleus. 1. Every carbon atom has 6 protons…2. Every neon atom has 10 protons…
B. On P.T. – located right above the chemical symbol
*Protons dictate the type of element we have**Electrons always equal the # of protons*
II. Atomic Number
A. Def – The sum of protons and neutrons in the nucleus of an atom.1. On P.T. – bottom number
-round up/down2. Ex: What is the mass number of the following elements?
Carbon OxygenIron CalciumSodium Zinc
III. Mass Number
12
56
23
16
40
65
3. Mass # = Protons + Neutrons
4. How many Neutrons on average are found in the following elements?Boron FluorineSilicon CopperSilver Gold118
14
6
61
10
35
A. Def – An atom that has a different number of neutrons.1. Does not affect the element2. Only changes the weight of the element
3. Ex: Boron-10 and Boron-11
IV. Isotope
p p p p p p p p p p
n n n n nn n n n n n
5 protons 5 protons
5 neutrons 6 neutrons
This meansthe mass #
Boron-10 Boron-11
4. How many neutrons do the following isotopes have?
Oxygen-14Titanium-50Magnesium-22Potassium-43Aluminum-23Iodine-130
6
28
10
24
10
77
A. Def – average mass of all isotopes of one element combined.1. Found on P.T. underneath chemical symbol.2. Ex: Carbon = 12.011
“Carbon has 3 known isotopes. Carbon-12, 13, and 14. Carbon-12 makes up
99% of all carbon on earth. Carbon-13 and 14 make up 1%.”
III. Average Atomic Mass
Chapter 4Lesson 3
“Modern Atomic Theory”
Chemistry Timeline…pg. 114-115
A. Def – a specific area where an electron is likely to be.
I. Bohr’s Model / Energy Levels
nucleus
2 electrons
8 electrons
18 electrons
32 electrons
e- e-
e-
e-
e-
e-
e-
e-
e-e-
e- e-e-
e-
e-
e-
e-
e-e-
e-
e-
e-e-e-
e-
e-
e-
e-
e-e-
e-
e- e-e-
e-
e-
e-
e-e-e-
e-e-
e-e-
e-e-e-e-
e-e-
e-e-
e-e-
e-
e-
e-e-
e-e-
Energy Level Maximum # of Electrons
1
2
3
4
2
8
18
32
Electrons in Energy Levels
1. Draw a picture of the following atoms with the correct number of e’s, p’s, and n’s…a. Na d. Heb. Al e. Cc. K f. S
2. Assign: Read pg. 118 and 1193. What is the difference between a ground
state and an excited state?
In Class Assignment
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