Chapter 2 – Matter is Made up of Atoms
I. Atoms and Their Structure
A. Early Ideas About Matter1. Greek philosophers proposed that matter was a combination of
the four fundamental elements: air, earth, fire, and water.
2. Debated whether matter could be continuously divided or
if there was an ultimate smallest piece.
3. Democritus proposed the world was made up of empty
space and tiny particles called atoms. This was the
foundation of the atomic theory.
B. Development of the Modern Atomic Theory
1. Law of Conservation of Mass- Antoine Lavoisier
2. Law of Definite Proportions – Joseph Proust
C. Dalton’s Atomic Theory
1. John Dalton studied the conclusions of the scientists above
and purposed the atomic theory explained the evidence.
2. Three main statements of Dalton’s Atomic Theory:
a. All matter is made up of atoms.
b. Atoms are indivisible and cannot be divided into
smaller particles.
c. All atoms of one element are alike, but they are
different from atoms of other elements.
D. Atomic Theory, Conservation of Matter, and Recycling
E. Hypothesis, Theories, and Laws
1. Hypothesis (noun)2. Theory (noun)3. Scientific law (noun)1
II. The Discovery of Atomic Structure
A. The Electron1. J.J. Thompson
2. Robert Milliken
B. Protons and Neutrons1. Rutherford’s Gold Foil Experiment
C. The Nuclear Model of the Atom
a. Nucleus:
b. Outside of the nucleus:
Particle
Symbols
Relative
Electric
Charge
Mass
Number
(A)
Relative
Mass
(amu)
Actual Mass (g)
Electron
Proton
Neutron
III. Atomic Numbers and Masses
A. Atomic Number (Z) –
1. Every element has a different atomic number…this identifies the
element!
2. Found on the periodic table…in each element block near the
symbol of the element
3. In a neutral atom, there will be
2
B. Mass Number (A) –
1. MUST BE GIVEN TO YOU!!! NOT on the periodic table!
2. Atoms of the same element may have different numbers of
neutrons, and therefore, different mass numbers.
a. These atoms are referred to as isotopes …
b. Although isotopes have different masses, they do not
significantly differ in chemical behavior.
Protium (Most
common form of
H…
99.985%)
Deuterium
“Heavy Hydrogen”
(0.015%)
Tritium
“Radioactive
Hydrogen”
(trace)
#
protons
#
neutrons
Mass
Number
3. Designating Isotopes
a. Nuclear Symbol
b. Hyphen Notation
4. Using either designation, one can determine the number of
protons, neutrons, and electrons…
a.
# protons = atomic number (Z) = # electrons
a.
# neutrons =
3
5. Examples
Nuclear
Symbol
Hyphen
Notation
#
Protons
#
Neutrons
#
Electrons
20
21
20
35Cl
131I
Uranium-235
C. Average Atomic Mass –
4
IV. Electrons in Atoms
A. Electrons in Motion
1. Energy
B. Electromagnetic Spectrum
1. Waves Transfer Energy
C. Electrons and Light
1. Evidence for Energy Levels
2. Electron Cloud Model
3. Electrons in Energy Levels
4. Lewis Dot Diagrams
Academic Words
Conclusion
Evidence
Contribute
Review
Modify
Adapt
Examine
Domain Specific Words
1. Atom
2. Atomic number
3. Atomic theory
4. Electron
5. Energy level
6. Isotope
7. Law of definite proportions
8. Law of conservation of mass
9. Lewis dot diagrams
10. Mass number
11. Neutron
12. Nucleus
5
13. Proton
14. Valence electron
6