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Atomic Theory Use with chapter #4 A Brief History.

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Presentation on theme: "Atomic Theory Use with chapter #4 A Brief History."— Presentation transcript:

1 Atomic Theory Use with chapter #4 A Brief History

2 Democritus (circa. 400 B.C.) Matter is made of empty space and tiny particles called “atoms.” Atoms are indivisible. There are different types of atoms for each material in the world.

3 Western Philosophy Pre-Socratic philosophy
Democritus Full name Born ca. 460 BCE Abdera Died ca. 370 BCE School/tradition Pre-Socratic philosophy Main interests metaphysics / mathematics / astronomy Notable ideas atomism, distant star theory

4 Aristotle (circa. 400 B.C.) Matter is not made of particles, but rather is continuous. Matter is made of earth, air, fire, and water.

5 Western philosophy Ancient philosophy
Marble bust of Aristotle. Roman copy after a Greek bronze original by Lysippus c. 330 BC. The alabaster mantle is modern Full name Ἀριστοτέλης, Aristotélēs Born 384 BCE Stageira, Chalcidice Died 322 BCE Euboea School/tradition Peripatetic school Aristotelianism Main interests Physics, Metaphysics, Poetry, Theatre, Music, Rhetoric, Politics, Government, Ethics, Biology, Zoology Notable ideas Golden mean, Reason, Logic, Passion

6 Why was Democritus Ignored?
Because the early Greek philosophers did not experiment and because Aristotle was an established teacher.

7 John Dalton (early 1800’s) Matter consists of tiny particles called atoms which are indivisible and indestructible. All atoms of a particular element are identical. Each element has different atoms. Atoms combine in whole number ratios to form compound atoms. In chemical reactions, atoms are combined, separated, or rearranged but are never created, destroyed, or changed.

8 Why were Dalton’s views accepted?
The scientific method is now the proper way to “do science.” Dalton’s theory was based on experimental observations: the law of Conservation of Mass and the law of Definite Proportions. Dalton’s theory correctly predicted the outcome of future experiments. These predictions became the law of Multiple Proportions.

9 The following statements match principles of Dalton’s theory
The following statements match principles of Dalton’s theory. List the principle that explains each statement. When methane burns, it combines with oxygen in the air to form molecules of water and carbon dioxide. Matter can never really be thrown away. That is one reason that recycling is important. The formula for ethanol is C2H6O, and the formula for acetic acid in vinegar is C2H4O2. Zinc is a softer metal than iron, and it reacts more readily with acid than iron does. There is no difference between copper found in an ancient Mayan necklace and copper wire freshly made from copper ore.

10 J.J. Thomson (late 1890’s) Problem: Required too many electrons!
Plum Pudding Model! All atoms contain negatively charged particles called electrons. All electrons are alike. Electrons exist in a “pudding” of positive charge. Problem: Required too many electrons!

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12 Robert Milliken (early 1900’s)
Oil Drop Experiment Determined Quantity of negative charge of the electron The charge to mass ratio of the electron Produced small droplets of negatively charged oil between to charged plates. The droplets could be suspended by apply a certain charge to the plates.

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14 Lord Rutherford (early 1900’s)
Each atom has a very tiny nucleus. The nucleus is positively charged. The electrons travel around the nucleus. The atom is mostly empty space. How Sent alpha particles through a thin sheet of gold Expected to pass right through, instead some were deflected at great angles End day 9 with this slide Problem: Electrons should spiral into the nucleus.

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18 Neils Bohr (early 1900’s) Problem: Model only works for hydrogen.
Atom contains positive nucleus. Electrons travel around the nucleus in specific energy levels. Electrons do not radiate energy in their normal energy level called the ground state. Electrons absorb energy and move to energy levels further from the nucleus called excited states. Electrons lose energy (light) as they return to lower energy levels. Problem: Model only works for hydrogen.

19 The Bohr Atom - Independent Practice: Read pages 107-112
Light Excited States - + Ground State Nucleus Independent Practice: Read pages Complete the Atomic Structure Multiple Choice worksheet

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