History of the Atomic Theory

The End!

What's next...Atomic Models

Video Review

"Who's Who in the Atomic Theory"

Early Scientists & Their Thoughts

A. History

General Idea:

Atom is a sphere

image from atomicmodel.tripod.com

Democritus, 400 B.C. proposed that the world was made up of two things:

1. Empty space

2. Small particles he called atoms (which is tiny indivisible particles)

His Views were not supported

Isaac Newton

Image from scienceworld.wolfram.com

Robert Boyle

Image from www.history.mcs.st-and.ac.uk

Isaac Newton and Robert Boyle in the 17th century published articles stating their belief in atomic structure.

ASSESSMENT

On-Line QUIZ: Atomic History

Development of the Atomic Theory, Zack & Jake Simons, www.youtube.com/watch?v=eXdWInBIncM

Directions:

• Select the Quiz button on the right of the screen.
• Due date: tba

Dalton's Atomic Theory

Quanta.org.in, Google Images, Web, 1 Dec 2012

B. Dalton’s Atomic Theory

John Dalton in the early 1800s offered the first logical quantitative explanation of atomic structure.

1. All matter is composed of tiny particles called atoms. *These particles could not be broken down into smaller substances.

2. Atoms of an element were exactly alike and atoms of different elements were unalike.

3. Atoms combine in simple ratios to form compounds. (law of definite and multiple proportions)

4. Atoms can not be destroyed (only rearranged during a chemical reaction)

image from chsd.us

John Dalton

Image from knarf.english.upenn.edu

History of the

Atomic Theory

Atoms can not be created nor

destroyed only rearranged

kosasihiskandarsjdn (2008 Jan 11) Cathode Ray Tube and Electron retrieved 2012 Dec 1 from www.youtube.com/watch?v=XU8nMKkzbT8

Research and Revisions of Dalton’s Atomic Theory - JJ Thompson

Watch - Music Video

"Introduction of the

Atomic Theory"

JJ Thomson - Plum Pudding - Electrons

Cathode Ray Tube:

High voltage electricity is passed into the cathode (negative end). A ray is generated toward the anode (positive end). When a magnet is placed near the ray, the negative end of magnet would cause the ray to bend in the opposite direction and the positive end would bend the ray towards the magnet.

Research and Revisions of Dalton’s Atomic Theory - JJ Thompson

Atomic Theory - Laws

ASSIGNMENT

Worksheet - History of Atomic Structure

tutorvista.com

D. Atomic Theory Early Laws

Atomic Theory Song Chemistry, cdawg131415, www.youtube.com/watch?v=07yDiELe83Y

Law of Conservation of Mass = matter cannot be created nor destroyed, only chemically altered.

A + B =  AB.

Thomson work with the cathode ray tube led to the discovery that cathode rays consisted of electrons.

By exposing the ray to a magnetic field and measuring the bending of the ray, he was able to calculate the ratio of an electron’s charge to its mass.

Cathode Ray Tube & Electron, kosasihiskandarsjdn, www.youtube.com/watch?v=XU8nMKkzbT8

D. Atomic Theory Early Laws

Law of Definite Proportions = specific substances always contain elements in the same ratio by mass.

Research and Revisions of Dalton’s Atomic Theory

JJ Thompson - Cathode Tube

Image from grantscienceworld.com

EX: mass of sodium to the mass of chlorine

in salt is always the same.

yourdictionary.com

D. Atomic Theory Early Laws

1. Plum Pudding Model using the Cathode Ray Tube

JJ Thomson proposed the Plum Pudding Model in which the negative electrons were held in place by a random scattering of positive charges.

Salt (Sodium Chloride)Molecule

Image from chemistry.wustl.edu

Law of Multiple Proportions = ratio of masses of one element that combine with a constant mass of another element can be expressed in small whole numbers.

EX: Tin (II) oxide = SnO = 1:1 ratio

Water = H2O = 2:1 ratio

Directions:

• Open the PDF on the right of the screen.
• Print off the assignment.
• Follow the directions on the worksheet.
• Due date: tba

water molecule

Image from scientopia.org

Gold Foil Experiment

Protons & Neutrons

Research and Revision of Dalton’s Atomic Theory

2. Rutherford’s Gold Experiment

Rutherford predicted the presence of neutrons in the nucleus.

Atoms are made of electrons

Rutherford's Muclear Atom Experiment, HerrPingui, www.youtube.com/watch?v=5pZj0u_XMbc

Results of Gold Foil Experiment

Most of the alpha particles are passing through the foil. A few are slightly deflected while even fewer are greatly deflected.

1. The atom contains a tiny dense center called the nucleus the volume is about 1/10 trillionth the volume of the atom

2. The nucleus is essentially the entire mass of the atom

3. The nucleus is positively charged the amount of positive charge of the nucleus balances the negative charge of the electrons

4. The electrons move around in the empty space of the atom surrounding the nucleus

ASSIGNMENT

Simulation - Rutherford's Atomic Theory

Directions:

• Open the PDF by clicking on the image on the right of the screen.
• Print off the assignment.
• Follow the directions on the worksheet.
• Due date: tba

By: Kenya Jackson