Atomic Structure

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Slide 1

Atomic Structure

Image courtesy of www.lab-initio.com

Slide 2

Chemistry Timeline

#1

B.C.

400 B.C. Demokritos and Leucippos use the term "atomos”

1500's

Georg Bauer: systematic metallurgy

Paracelsus: medicinal application of minerals

1600's

Robert Boyle:The Skeptical Chemist. Quantitative experimentation, identification of

elements

1700s'

Georg Stahl: Phlogiston Theory

Joseph Priestly: Discovery of oxygen

Antoine Lavoisier: The role of oxygen in combustion, law of conservation of

mass, first modern chemistry textbook

 2000 years of Alchemy

Slide 3

Chemistry Timeline #2

1800's

Joseph Proust: The law of definite proportion (composition)

John Dalton: The Atomic Theory, The law of multiple proportions

Joseph Gay-Lussac: Combining volumes of gases, existence of diatomic molecules

Amadeo Avogadro: Molar volumes of gases

Jons Jakob Berzelius: Relative atomic masses, modern symbols for the elements

Dmitri Mendeleyev: The periodic table

J.J. Thomson: discovery of the electron

Henri Becquerel: Discovery of radioactivity

1900's

Robert Millikan: Charge and mass of the electron

Ernest Rutherford: Existence of the nucleus, and its relative size

Meitner & Fermi: Sustained nuclear fission

Ernest Lawrence: The cyclotron and trans-uranium elements

Slide 4

Dalton’s Atomic Theory (1808)

Atoms cannot be subdivided, created, or destroyed

Atoms of different elements combine in simple whole-number ratios to form chemical compounds

In chemical reactions, atoms are combined, separated, or rearranged

All matter is composed of extremely small particles called atoms

Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties

John Dalton

Slide 5

Modern Atomic Theory

Several changes have been made to Dalton’s theory.

Dalton said:

Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties

Modern theory states:

Atoms of an element have a characteristic average mass which is unique to that element.

Slide 6

Modern Atomic Theory #2

Dalton said:

Modern theory states:

Atoms cannot be subdivided, created, or destroyed

Atoms cannot be subdivided, created, or destroyed in ordinary chemical reactions. However, these changes CAN occur in nuclear reactions