ATOMIC THEORY TIMELINE

DEMOCRITUS

• 460 BC - 370 BC
• Central figure in the development of the atomic theory
• Ancient Greek philosopher
• Mentored by Leucippus
• Studied and traveled to many places

DEMOCRITUS' ATOMIC THEORY

• All matter consists of atoms
• Atoms are indestructible
• Atoms are solid and invisible
• Atoms are homogenous
• Atoms differ in size,shape,mass,position, arrangement

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ANTOINE LAVOISIER (1743-1794)

• "The father of modern chemistry"
• A french noblemen and chemist
• Helped construct the metric system
• Was executed in the french revolution
• Was recognized by many important people

CONTRIBUTIONS:

• Demonstrated that air is composed of two parts
• showed the phlogiston theory to be inconsistent
• contributed to early ideas on composition and chemical changes by stating the radical theory
• reinforced his own quantitative experiments
• introduced the possibility of allotropy in chemical elements

SET UP:

JOHN DALTON (1766-1844)

• identified the hereditary nature of red-green color blindness
• allowed for the cost-efficient manufacturing of chemical compounds
• Granted several awards and created laws
• Contributed to modern science
• In 1803 he revealed the concept of Dalton’s Law of Partial Pressures

ATOMIC THEORY

• All matter is made of atoms. Atoms are indivisible and indestructible.
• All atoms of a given element are identical in mass and properties
• Compounds are formed by a combination of two or more different kinds of atoms.
• A chemical reaction is a rearrangement of atoms.

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ROBERT MILLIKAN(1868-1953)

• honored with the Nobel Prize for Physics
• Made a series of experiments to determine the electric charge carried by a single electron
• Setteld the charge-to-mass ratio
• His experiments also aided both Einstein and Bohr
• explored the photoelectric effect

MODEL:

JAMES CHADWICK(1891-1974)

• Established the atomic number
• Discovered the neutron in the atom

MODEL:

CATHODE RAY TUBE(1897)

• vacuum tube containing one or more electron guns, and a fluorescent screen used to view images.
• accelerate and deflect the electron beam onto the screen to create the images
• Created by J.J Thomson
• can emit a small amount of X-ray radiation
• heavy and bulky and take up a lot of space

J.J THOMSON (1856-1940)

• English Physicist
• Elected as a fellow of the royal society of London
• Appointed to the Cavendish Professorship of Experimental Physics
• Awarded with the 1906 Nobel Prize in Physics
• Presented ideas in the atomic structure

THOMSON ATOMIC THEORY:

• Electrons travel in a straight line
• Electrons have momentum and kinetic energy
• Electrons travel with high velocities
• Electrons produce heat when they strike
• Electrons produce florescence when theubstrike certain mediums

THOMSON'S EXPERIMENT

PLUM PUDDING ATOMIC MODEL(1904)

• Proposed by J.J Thomson
• Electrons are surronded by positively charged particles
• This was proved wrong

GOLD FOIL EXPERIMENT(1900'S)

• Rutherford's Experiment
• every atom contains a nucleus where its positive charge and most of its mass is concentrated
• Some particles were bounced back when sent through a atom

BOHR PLANETARY MODEL

• proposed by Niels Bohr in 1915
• It is not all the way correct
• Positively charged nucleus
• relatively primitive model of the hydrogen atom
• first-order approximation of the hydrogen atom