History of the Atom Model 450 BC Democritus (Greek)- World was made of 2 things: 1.Empty space...

History of the Atom Model

450 BC

Democritus (Greek)- World was made of 2 things:1. Empty space2. Tiny particles call atoms

(Atomus= indivisible)

Aristotle (Greek)- Matter is continuous and not made of smaller particles

PROBLEM: Neither had any evidence.

Air, earth, fire & water

History of the Atom Model

Antonine Lavoisier (French)-1782

Law of Conservation of Matter (mass)

Matter is neither created Nor destroyed, it is only rearranged.

Mass of reactants = Mass of products

History of the Atom Model

Joseph Proust (French)-1799

Law of Definite Proportions

Atoms must combine in whole number ratios.

H20 vs H0 ½

History of the Atom Model

Joseph Proust (French)-1799

Law of Multiple Proportions

Atoms can combine in different

whole number ratios.

H20 vs H202

Modern Atomic Theory (MAT) Developing

1803 John Dalton (English)-

“Father of Modern Atomic Theory”

Started teaching at 12 years old.

Dalton’s Atomic Theory

1. All matter is made up of atoms. Atoms are the smallest fundamental units of matter.

Dalton’s Atomic Theory

1. All matter is made up of atoms. Atoms are the smallest fundamental units of matter.

TRUE

Dalton’s Atomic Theory

1. All matter is made up of atoms. Atoms are the smallest fundamental units of matter.

2. All elements consist of atoms which are indivisible & indestructible.

TRUE

Dalton’s Atomic Theory

1. All matter is made up of atoms. Atoms are the smallest fundamental units of matter.

2. All elements consist of atoms which are indivisible & indestructible.

TRUE

FALSENuclear reactions

Dalton’s Atomic Theory1. All matter is made up of atoms. Atoms are the smallest

fundamental units of matter.

2. All elements consist of atoms which are indivisible &

indestructible.

3. All atoms of the same element are identical in size, shape & mass.

TRUE

FALSE

Nuclear reactions

Dalton’s Atomic Theory1. All matter is made up of atoms. Atoms are the smallest

fundamental units of matter.

2. All elements consist of atoms which are indivisible &

indestructible.

3. All atoms of the same element are identical in size, shape & mass.

TRUE

FALSE

Nuclear reactions

FALSEIsotopes

Dalton’s Atomic Theory1. All matter is made up of atoms. Atoms are

the smallest fundamental units of matter.

2. All elements consist of atoms which are

indivisible & indestructible. 3. All atoms of the same element are identical in

size, shape & mass.

4. Atoms of different elements are different in size, shape, & mass.

TRUE

FALSE

Nuclear reactions

FALSE

Isotopes

Dalton’s Atomic Theory1. All matter is made up of atoms. Atoms are

the smallest fundamental units of matter.

2. All elements consist of atoms which are

indivisible & indestructible. 3. All atoms of the same element are identical in

size, shape & mass.

4. Atoms of different elements are different in size, shape, & mass.

TRUE

FALSE

Nuclear reactions

FALSE

Isotopes

TRUE

Dalton’s Atomic Theory1. All matter is made up of atoms. Atoms are the smallest fundamental

units of matter.

2. All elements consist of atoms which are indivisible & indestructible.

3. All atoms of the same element are identical in size, shape & mass.

4. Atoms of different elements are different in size, shape, & mass.

5. In a chemical reaction, atoms are rearranged, never created nor destroyed & they combine in whole number ratios.

TRUE

FALSE

FALSE

TRUE

Dalton’s Atomic Theory1. All matter is made up of atoms. Atoms are the smallest fundamental

units of matter.

2. All elements consist of atoms which are indivisible & indestructible.

3. All atoms of the same element are identical in size, shape & mass.

4. Atoms of different elements are different in size, shape, & mass.

5. In a chemical reaction, atoms are rearranged, never created nor destroyed & they combine in whole number ratios.

TRUE

FALSE

FALSE

TRUE

TRUE

Dalton’s Atomic Model

Modern Atomic Theory (MAT) Developing

Michael Faraday (English)-1839

Atomic structure might be related to electricity…it might have a charge.

Ben Franklin (English)-

2 types of charges• Positive (later proton)• Negative (later electron)

Problem with Dalton’s Atom Model?

Lacks subatomic particles…

Modern Atomic Theory (MAT) Developing

JJ Thomson (English)-1897

Cathode Ray Tube Experiment

link

Thomson’s Plum-Pudding Model

- ++ + -

+ - + -+ -

- +- +

-+ + + +- +

- +-+

Protons & Electrons

Lots of empty space

Problem with Plum-Pudding Model?

- ++ + -

+ - + -+ -

- +- +

-+ + + +- +

- +-+

+ and - attract- +

+- +- + - +-+ -- +- +-+-

+ - +-++-+- +-+

Modern Atomic Theory (MAT) Developing

Ernest Rutherford (English)1909

Gold Foil Experiment

link

Modern Atomic Theory (MAT) Developing

The Results & The Explanation

• Most of positive charges passed through because the atom is mostly empty space.

• Some of the positive charges deflected because the atom contains some positive charge.• Some of positive charges deflected straightback because there is a concentrated area of positive charge (nucleus).

Rutherford’s Atomic Model

Nucleus- Contains Protons

Electrons surround nucleus

Lots of empty space

_+++

+++++++

_

__

_

_

_

_

Problem with Rutherford’s Model?

+ and - attract_

++++++++++

_

__

_

_

_

_

++++++++++

_

_

_

__

_

_

Modern Atomic Theory (MAT) Developing

Niels Bohr (American)-1913

Solar System Model-

Electrons are like planets that orbit the nucleus

link

Problem with Solar System Model?

Scientists found this model failed for atoms other than Hydrogen because it couldn’t predict the energy levels of electrons in atoms with more than one electron.

Modern Atomic Theory (MAT) Developing

Louis de Broglie (French physicist)-1924

Wave and particle Model-

1926 Werner Heisenberg (German physicist)-

Uncertainty Principle

Modern Atomic Theory (MAT) Developing

Erwin Schrodinger-

(Austrian Physicist)1926

Charge Cloud Model-

•Basic Parts of the Atom Nucleus Electron Cloud

link

ATOM ATOM COMPOSITIONCOMPOSITION

•protons and neutrons in protons and neutrons in the nucleus.the nucleus.

•the number of electrons is equal to the the number of electrons is equal to the number of protons.number of protons.

•electrons in space around the nucleus.electrons in space around the nucleus.

•extremely small. One teaspoon of water has extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean 3 times as many atoms as the Atlantic Ocean has teaspoons of water.has teaspoons of water.

The atom is mostlyThe atom is mostlyempty spaceempty space

Nucleus is Very Massive

nn

nn

n n

• Protons - Positive Charge

• Neutrons - Neutral

• Electrons - Negative