Title: Chapter 5 Early Atomic Theory and Structure
1Chapter 5Early Atomic Theory and Structure
2Objectives
- History of Atomic Theory (5.1-5.5, 5.7)
- Subatomic Particles (5.5, 5.8)
- Atomic Numbers (5.9)
- Isotopes (5.10)
- Atomic Mass (5.11)
3Democritus of Abdera
- 460 BC to 370 BC
- World made of empty space and tiny particles
called atoms - Student of Leucippus
4Democritus of Abdera
- All matter is composed of atoms, which are bits
of matter too small to be seen. These atoms
CANNOT be further split into smaller portions - There is a void, which is empty space between
atoms - Atoms are completely solid
- Atoms are homogenous, with no internal structure
- Atoms differ in size, shape and weight
5Aristotle
- Opposed ideas of Democritus
- Empedoclean theory
- 4 elements
- Earth, air, fire, water
- Ideas dominate into 17th century
6Atomism in Antiquity
- Church spoke against atoms
- Did not support God creating earth
7Atomism in the Middle Ages
- Artistotles works rediscovered (1200s)
- Catholic Church
- Atomic thinking Godlessness
- De Rerum Natura rediscovered in 1417
- Prime source for ideas of Leucippus and Democritus
8Atomism in the Renaissance
- Dominated by Alchemists
- Mystics, fakes
- Turning cheap metal into gold
- Discovery of many elements
- Preparation of mineral acids
9Robert Boyle (1627-1691)
- Matter is divided into little particles of
several sizes (corpuscles) - First to perform truly quantitative experiments
- Pressure and volume of air
10Antoine Laurent LavoisierFather of Chemistry
- 1743-1794
- Matter can be changed but never created or
destroyed - Law of Conservation of Mass
11Antoine Laurent LavoisierFather of Chemistry
"It took them only an instant to cut off that
head, and a hundred years may not produce another
like it."
12Amadeo Avogadro
- (1776-1856)
- Equal volumes of gases, under the same
conditions, have the same number of molecules
13John Dalton
- (1766-1844)
- Englishman
- School teacher
- Developed atomic theory
14John Dalton
- All matter is composed of atoms
- Atoms of the same element are identical
- Atoms cannot be subdivided, created or destroyed
15John Dalton
4. Atoms of different elements combine in small
whole numbers 5. In chemical reactions, atoms are
combined, separated or rearranged
16John Dalton
Law of Multiple Proportions When two elements
form a series of compounds, the ratios of the
masses of the second element that combine with 1
gram of the first element can always be reduced
to small whole numbers CO, CO2, CO3, etc.
17J. J. Thomson
- 1856-1940
- Showed experimentally the existence of the
electron
18J. J. Thomson
19J. J. Thomson
20Robert A. Millikan
- Determined charge of an electron
- Negative
21Ernest Rutherford
- 1871-1937
- Defined radioactivity
- Named alpha and beta particles
22Ernest Rutherford
23Ernest Rutherford
24The Modern Day Atom
- Nucleus
- Positively charged protons
- Neutral neutrons
- Orbiting Nucleus
- Negatively charged electrons
25Atomic Numbers (Z)
- Equal to number of protons in the nucleus
- NEVER CHANGES
26Mass Number (A)
- Sum of protons and neutrons in the nucleus
27Isotopes of the Elements
- Same atomic number but different atomic masses
- Different number of neutrons
28Ions of the Elements
- Same number of protons and neutrons
- Has lost or gained electrons
- Contains charge
29Atomic Mass
- Measured in atomic mass units
- Equal to exactly 1/12 mass of a carbon-12 atom
- Average relative mass of the isotopes of that
element compared to the atomic mass of carbon-12 - Average atomic mass (seen on periodic table)
- Atomic mass of each isotope x fraction present
- Add all.
- See pg 95