1. The atom’s history and theories

2. Hill, J. and D. Kolb. 1995. Chemistry for Changing Times 7th ed
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. p.36
“A pool of water can be separated into drops, and then each drop can be split into smaller and smaller drops. Suppose you could keep splitting these drops into still smaller ones even after they became much too small to see. Would you ever reach the point at which the tiny drop could no longer be separated into smaller droplets of water?”
What's the size of
water?
media.nasaexplores.com/.../images/faucet2.jpg

3. Look at the sand at the beach!
Early History
There must be ultimate tiny particles of water that could not be further subdivided.
Look at the sand at the beach!
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. p.36
“Leucippus, the Greek philosopher, and his pupil Democritus might well have discussed this question as they strolled along the beach of the Aegean Sea back in the fifth century B.C. Based on his intuition, Leucippus felt that there must be ultimate tiny particles of water that could not be subdivided.”
Leucippus
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc.

4. These atoms are distinct in shape and size!
Early History
I’ll name these indivisible particles atomos (which means indivisible).
These atoms are distinct in shape and size!
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. p.36
“Democritus expanded on this idea of Leucippus and gave the tiny particles a name. He described them as “atomos” (indivisible). We still refer to the tiny unit particles of elements as atoms. Democritus believed that each kind of atom was distinct in shape and size. Real substances were thought to be mixtures of various kinds of atoms.”
460 – 370 BC
Democritus
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc.
web.mit.edu/philos/www/mm/democritus.jpg

5. There are only four elements!
Early History
There are only four elements!
Earth
Water
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. p.36
“The Greeks at that time believed that there were four basic elements: earth, air, fire, and water.”
“Democritus imagined that “atoms” of water might be smooth round balls and that “atoms” of fire could have sharp edges.”
“Five centuries later the Roman poet Lucretius wrote his long “On the Nature of Things,” in which he gave strong arguments for the atomic nature of matter. But a few centuries earlier Aristotle had declared that matter was continuous, not atomistic, and the ancient Greeks and Romans had no way to determine which of these two views of matter was correct. The ancients almost never used experimentation, preferring instead to use reason and logic. The continuous view of matter seemed more logical and reasonable to most of them, and so they accepted the view of Aristotle, which prevailed for 2000 years, even though it was wrong.”
Air
Fire
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc.

6. Law of Conservation of Mass
When a chemical reaction is carried out in a closed system, the total mass of the system does not change!
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. p. 37
“By about A.D. 1700, scientists were observing more carefully and measuring more accurately. Antoine Laurent Lavoisier, a Frenchman, perhaps did more than anyone else to establish chemistry as a quantitative science”, that is why he is considered to be the father of modern chemistry
1743 – 1794
Antoine Lavoisier
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc.

7. Law of Conservation of Mass: The total mass of the system does not change
product
reactant reactant 2 =
calcium oxide + carbon dioxide
calcium carbonate
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. p.37
“Lavoisier carried out many experiments.”
“Lavoisier summarized his findings in a scientific law (Law of Conservation of mass)
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill. P. 7
“After a large amount of data have been collected, it is often desirable to summarize the information in a concise way, as a [scientific] law.”
scientific laws – brief statement summarizing the patterns observed in many scientific data
“What is known is that the carbon cycle must be a closed system; in other words, there is a fixed amount of carbon in the world and it must be somewhere”
The resources of the world are limited/fixed. That is why there is a need to reduce, reuse and recycle.
56.08 g g g
Silberberg, M Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.

8. Law of Definite Composition
A given compound always contains its constituent elements in certain fixed proportions by mass!
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. p. 38
“By the end of the 18th century, Lavoisier and other scientists noted that many substances were composed of two or more elements. Each compound had the same elements in the same proportions, regardless of where the compound came from or who prepared it. The painstaking work of Proust convinced most chemists of the general validity of these observations.”
Proust
1754 – 1826
Silberberg, M Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.

9. Law of Definite Composition: No matter the mode of preparation, a particular compound is composed of the same elements in the same mass fractions
10.00 g lead
11.56 g lead sulfide
1.56 g sulfur
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. p
“One of the earliest illustrations of the law of definite proportions is found in the work of the noted Swedish chemist J.J. Berzelius ( ). Berzelius heated g of lead with various amounts of sulfur to form lead sulfide. Lead is a soft, grayish metal. Sulfur is a yellow solid. Lead sulfide is a shiny, black solid. It is easy, therefore, to tell when all the lead had reacted.”
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc.

10. Law of Definite Composition: No matter the mode of preparation, a particular compound is composed of the same elements in the same mass fractions
10.00 g lead
11.56 g lead sulfide
3.00 g sulfur
1.44 g sulfur left-over
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc.

11. Law of Definite Composition: No matter the mode of preparation, a particular compound is composed of the same elements in the same mass fractions
11.56 g lead sulfide
18.00 g lead
1.56 g sulfur
8.00 g lead left-over
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc.

12. Law of Definite Composition: No matter the source, a particular compound is composed of the same elements in the same mass fractions
Analysis by Mass
(grams/20.0 g)
Mass Fraction
(parts/1.00 part)
8.0 g calcium
2.4 g carbon
9.6 g oxygen
0.40 calcium
0.12 carbon
0.48 oxygen
Silberberg, M Principles of General Chemistry. 2nd ed. New York: McGraw-Hill. p. 35
“Law of definite composition. Calcium carbonate is found naturally in many forms, including marble (top), coral (bottom), chalk, and seashells. The mass percents of its component elements do not change regardless of the compound’s source”
20.0 g
1.00 part by mass
Silberberg, M Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.

13. Law of Multiple Proportions
Elements can combine in more than one set of proportions, and each set corresponds to a different compound!
Dalton
1766 – 1884
Hill, J. and D. Kolb Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc.

14. Law of Multiple Proportions: Elements can combine in more than one set of proportions
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill.
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill. p. 37
“Different compounds made up of the same elements differ in the number of atoms of each kind that combine. For example, carbon forms two stable compounds with oxygen, namely carbon monoxide and carbon dioxide. Modern measurement techniques indicate that one atom of carbon combines with one atom of oxygen in carbon monoxide and with two atoms of oxygen in carbon dioxide. Thus, the ratio of oxygen in carbon monoxide to oxygen in carbon dioxide is 1:2”

15. Atomic Theory
Elements are composed of extremely small particles called atoms. All atoms of a given element are identical, having the same size, mass, and chemical properties. The atoms of one element are different from the atoms of all other elements.
Hill, J. and Petrucci, R General Chemistry Instructor’s Edition.USA: Prentice-Hall, Inc.
scientific laws – brief statement summarizing the patterns observed in many scientific data
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill. P. 41
theory – unifying principle that explains a body of facts and/or those laws that are based on them
Silberberg, M Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
“Dalton expressed his theory in a series of postulates. Like most great thinkers, Dalton incorporated the ideas of others into his own to create the new theory.” [that’s why this is called a theory. see law vs. theory as explained above]
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill. p. 36
“John Dalton formulated a precise definition of the indivisible building blocks of matter that we call atoms.”
“The first hypothesis states that atoms of one element are different from atoms of all other elements. Dalton made no attempt to describe the structure or composition of atoms – he had no idea what an atom is really like. But he did realize that the different properties shown by elements such as hydrogen and oxygen can be explained by assuming that hydrogen atoms are not the same as oxygen atoms.”
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill.

16. Atomic Theory
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill.

17. Law of Definite Composition Law of Multiple Proportions
Atomic Theory
Compounds are composed of atoms of more than one element. In any compound, the ratio of the numbers of atoms of any two of the elements present is either an integer or a simple fraction
Supports
Law of Definite Composition
Law of Multiple Proportions
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill. p. 37
“The second hypothesis suggests that, in order to form a certain compound, we need not only atoms of the right kinds of elements, but specific numbers of these atoms as well. This idea is an extension of [the] law of definite composition [by Proust]”
“[This] also supports the law of multiple proportions.”
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill.

18. Atomic Theory
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill.

19. Supports the Law of Conservation of Mass
Atomic Theory
A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction
Supports the Law of Conservation of Mass
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill. p. 37
“Dalton’s third hypothesis is another way of stating the law of conservation of mass. Since matter is made of atoms that are unchanged in a chemical reaction, it follows that mass must be conserved as well.”
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill.

20. Atomic Theory +
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill.

21. Based on Dalton’s Atomic Theory, the atom is
the basic unit of an element that can enter
into a chemical reaction
extremely small
indivisible
Chang, R Chemistry 7th ed. Singapore: McGraw-Hill.