How We Got To Where We Are Now!!

Atomic Theorists

Atomic TheoristsAt the conclusion of our time together, you should be able to:

1. List 5 major atomic theorists2. If possible, give a piece of equipment or

experiment for which they are noted3. Draw their model of the atom4. List 3 basic laws of chemistry that were used

to help develop the atomic theory

15 Helpful Hints On The Lab Report from

Mr. T’s Vast Lab Experience!!!

Hint #1. When you don't know what you are doing, do it neatly. 

Who: Democritus

• When: 400 B.C.• Where: Greece• What: Matter was made of indivisible

substances he called atomos (1st talk of the atom)

What: All matter is a combination offire, air, earth or water

When: 350 B.C.Where: Greece

Who: Aristotle

Who: Antoine Lavoisier

Matter can't be created or destroyed

When: 1785

Where: France

Law of Conservation of Mass

Who: Joseph ProustWhat: Elements – Compounds put

together in fixed ratios of small whole numbers

ex. C + O2 CO2

When: 1797

Where: France

Law of Definite Proportions

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Who: John DaltonWhat: Two elements can form more

than one compoundThe subscripts of the elements

in the compounds will be small whole numbers.

C + O2 CO2

C + O2 COWhere: EnglandWhen: 1803

Law of Multiple Proportions

2

2.1

What: Solid Sphere Model (1st atomic theory)

1. Matter is composed of indivisible particles2. All atoms of a particular element are identical 3. Different elements have different atoms 4. Atoms combine in certain whole-number ratios5. In a chemical reaction, atoms are merely

rearranged to form new compounds; they are not created, destroyed, or changed into atoms of any other elements.

Who: John Dalton

8 X2Y16 X 8 Y+

2.1

Problems with Dalton’s Theory

Problems with Dalton’s Atomic Theory?1. Matter is composed of indivisible

particlesAtoms can be divided, but only in a nuclear reaction

2. All atoms of a particular element are identical Does not account for isotopes (atoms of the same element but a different mass due to a different number of neutrons)!

3. Different elements have different atoms Yes!

4. Atoms combine in certain whole-number ratiosYes! Called the Law of Definite Proportions

5. In a chemical reaction, atoms are merely rearranged to form new compounds; they are not created, destroyed, or changed into atoms of any other elements. Yes, except for nuclear reactions

Remember to make clear and concise statements with your

observations!!!

What: Atoms are not the smallest particle

• Conducted experiment with a Cathode Ray Tube• Particles had a negative charge

(discovered electrons)• Model = plum pudding

jello fruit salad

When: 1897 Where: England

Who: J.J. Thomson

Cathode Ray Tube

J.J. Thomson, measured mass/charge of e-

(1906 Nobel Prize in Physics)

2.2

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What: • Experiments to determine mass of electron

• Conducted the oil drop experiment

• Verified that electron is negatively charged; 1.6 x 10 -19 coulombs

• No new model

Where: AmericaWhen: 1910

Who: Robert Millikan

Millikan’sOil Drop Experiment

e- charge = -1.60 x 10-19 CThomson’s charge/mass of e- = -1.76 x 108 C/g

e- mass = 9.10 x 10-28 g

Measured mass of e- (1923 Nobel Prize in

Physics)

2.2

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What:Conducted Gold Foil experimentProved nucleus is dense, positively

charged core of atom

When: 1911Where: America

Who: Ernest Rutherford

• Model = Stationary Planetary

Rutherford’s Experiment

Gold Foil Experiment

1. atoms positive charge is concentrated in the nucleus

2. proton (p) has opposite (+) charge of electron3. mass of p is 1840 x mass of e- (1.67 x 10-24 g)

a particle velocity ~ 1.4 x 107 m/s

(~5% speed of light)

(1908 Nobel Prize in Chemistry)

2.2

Results of foil experiment if Plum Pudding model had been correct.

What Actually Happened

atomic radius ~ 100 pm = 1 x 10-10 mnuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m

Rutherford’s Model of the Atom

2.2

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What: Pulsating Planetary Model

Electrons can move between energy levels

When: 1913Where: Denmark

Who: Niels Bohr

What:Confirmed existence of neutronNo new atomic model

When: 1932

Where: England

Who: James Chadwick

Chadwick’s Experiment (1932)

H atoms - 1 p; He atoms - 2 pmass He/mass H should = 2

measured mass He/mass H = 4

a + 9Be 1n + 12C + energy

neutron (n) is neutral (charge = 0)n mass ~ p mass = 1.67 x 10-24 g

2.2

Interesting Name for a Boat!!

Atomic TheoristsLet’s see if you can:

1. List 5 major atomic theorists2. If possible, give a piece of equipment or

experiment for which they are noted3. Draw their model of the atom4. List 3 basic laws of chemistry that were used

to help develop the atomic theory

Get Your Clicker!!!

The following diagram describes best the ideas of whom?

1. Aristotle2. John Dalton3. J J Thomson4. Ernest

Rutherford5. Democritus

What idea does the following diagram describe?

1. Solid Sphere Model

2. Stationary planetary model

3. Plum pudding model

4. Pulsating orbital model

Which law defines the following?H2 + O2 H2O2

H2 + O2 H2O

1. Law of conservation of mass

2. Law of definite proportions

3. Law of multiple proportions

Who is responsible for the following diagram?

1. Neils Bohr2. John Dalton 3. J J Thomson 4. Ernest Rutherford

5. Millikan

Who of the following contributors to the Atomic Theory would come 4th

on a time line?

1. Aristotle 2. John Dalton3. J J Thomson 4. Ernest Rutherford5. Democritus

Who used this piece of equipment to contribute to the Atomic Theory?

1. Neils Bohr 2. John Dalton 3. J J Thomson 4. Ernest Rutherford5. Millikan

1. Solid Sphere Model

2. Stationary planetary model

3. Plum pudding model

4. Pulsating orbital model

What does the following diagram describe?

WHY GOD MADE MOMSAnswers given by 2nd grade school children to the following  questions:

Why did God make mothers?

1.  She's the only one who knows where the scotch tape is.2.  Mostly to clean the house.3. To help us out of there when we were getting born.

Draw 4 historical models of atoms on a time-line. The correct model is one point, the correct name or person of the model is one point and the correct approximate time on the line is one point.

The Atom Historical Models Family Feud

Part of Atom

Size (Tennis B,

Base B, Nerf B)

Mass (Heaviest, Lightest, Middle)

Distance from

Center (meters)

ProtonNeutronElectron

The Modern Atom Family Feud