History of the Atom Model 450 BC Democritus

History of the Atom Model 450 BC Democritus (Greek)World was made of 2 things: 1. Empty space 2. Tiny particles call atoms (Atomus= indivisible) Air, earth, fire & water Aristotle (Greek)Matter is continuous and not made of smaller particles PROBLEM: Neither had any evidence.

History of the Atom Model 1782 Antonine Lavoisier (French)- 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 1799 Joseph Proust (French)- Law of Definite Proportions Atoms must combine in whole number ratios. H 20 vs H 0 ½

History of the Atom Model 1799 Joseph Proust (French)- Law of Multiple Proportions Atoms can combine in different whole number ratios. H 20 vs H 20 2

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

Dalton’s Atomic Theory TRUE 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.

Dalton’s Atomic Theory TRUE 1. All matter is made up of atoms. Atoms are the smallest fundamental units of matter. FALSE 2. All elements consist of atoms which are indivisible & Nuclear reactions indestructible.

Dalton’s Atomic Theory TRUE 1. FALSE 2. Nuclear reactions All matter is made up of atoms. Atoms are the smallest fundamental units of matter. All elements consist of atoms which are indivisible & indestructible. 3. All atoms of the same element are identical in size, shape & mass.

Dalton’s Atomic Theory TRUE 1. FALSE 2. Nuclear reactions FALSE Isotopes All matter is made up of atoms. Atoms are the smallest fundamental units of matter. All elements consist of atoms which are indivisible & indestructible. 3. All atoms of the same element are identical in size, shape & mass.

Dalton’s Atomic Theory TRUE FALSE Nuclear reactions FALSE Isotopes 1. 2. 3. All matter is made up of atoms. Atoms are the smallest fundamental units of matter. All elements consist of atoms which are indivisible & indestructible. All atoms of the same element are identical in size, shape & mass. 4. Atoms of different elements are different in size, shape, & mass.

Dalton’s Atomic Theory TRUE FALSE Nuclear reactions FALSE Isotopes TRUE 1. 2. 3. All matter is made up of atoms. Atoms are the smallest fundamental units of matter. All elements consist of atoms which are indivisible & indestructible. All atoms of the same element are identical in size, shape & mass. 4. Atoms of different elements are different in size, shape, & mass.

Dalton’s Atomic Theory TRUE 1. All matter is made up of atoms. Atoms are the smallest fundamental units of matter. FALSE 2. All elements consist of atoms which are indivisible & indestructible. FALSE 3. All atoms of the same element are identical in size, shape & mass TRUE 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. .

Dalton’s Atomic Theory TRUE 1. All matter is made up of atoms. Atoms are the smallest fundamental units of matter. FALSE 2. All elements consist of atoms which are indivisible & indestructible. FALSE 3. All atoms of the same element are identical in size, shape & mass TRUE 4. Atoms of different elements are different in size, shape, & mass. TRUE 5. In a chemical reaction, atoms are rearranged, never created nor destroyed & they combine in whole number ratios. .

Dalton’s Atomic Model

Modern Atomic Theory (MAT) Developing 1839 Michael Faraday (English)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 1909 Ernest Rutherford (English) 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 straight back 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 1924 Louis de Broglie (French physicist)Wave and particle Model- 1926 Werner Heisenberg (German physicist)- Uncertainty Principle

Modern Atomic Theory (MAT) Developing 1926 Erwin Schrodinger(Austrian Physicist) Charge Cloud Model- • Basic Parts of the Atom Nucleus Electron Cloud link

ATOM COMPOSITION The atom is mostly empty space • protons and neutrons in the nucleus. • the number of electrons is equal to the number of protons. • electrons in space around the nucleus. • extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water.

Nucleus is Very Massive • Protons - Positive Charge • Neutrons - Neutral • Electrons - Negative