Development of the Atomic Model

Question 1

Democritis

Answer 1

• Greek Philosopher
• First to identify the possiblity of an atom because he thought that matter is made of small particles
• He named these the “ultimate” particles atomos which means indivisible

Question 2

Aristotle

Answer 2

• Dismissed Democritis’ atom idea as worthless
• Believed in reasoning instead of scientific experiments
• Said there was always a smaller piece of mater, no matter the size
• Four “elements” of earth, fire, air, water
• Theory accepted for 2000 years

Question 3

Antione Laviosier

Answer 3

Law of Conservation of Mass - Matter is not create or destroyed, just changed in a reaction

Question 4

Joseph Proust

Answer 4

Law of Definite Proportions - Always have the same proportions of elements by mass

Question 5

John Dalton

Answer 5

• Father of modern atomic theory
• Model of solid sphere
• Law of Multiple Proportions
• Developed concept of the mole
• Proposed system of symbols

Question 6

J.J. Thomson

Answer 6

• Discovered electron in 1897
• Known for plum pudding model
• Cathode ray tube experiment
• Discovered isotopes of elements

Question 7

Eugene Goldstein

Answer 7

• Discovered protons in 1900
• Anode ray experiment
• Said that since atoms contain negatively charged particles, they must also contain positively charged particles in order to remain electrically neutral
• Supported Thomson’s Plum Pudding Model

Question 8

Max Planck

Answer 8

• Founder of quantum theory
• Atoms can emit “quanta”
• Einstein used his work to study photons
• Planck’s constant

Question 9

Robert Millikan

Answer 9

• Oil drop experiment
• Measured charge of electron
• Calculated mass of electron
• Worked with Thomson

Question 10

Ernest Rutherford

Answer 10

• Discovered atoms have a small positive nucleus and remainder is empty space
• Gold Foil Experiment
• Predicted existence of neutrons
• Worked for Thomson

Question 11

Francis Aston

Answer 11

• First person to observe isotopes
• His work led Rutherford to predict the existence of the neutron

Question 12

Neils Bohr

Answer 12

• Planetary model of atom
• Electrons move around the nucleus in fixed orbits, paths or energy levels
• Spectrum lines produced when electrons move

Question 13

Erwin Schrodinger

Answer 13

• Another founder of quantum mechanics
• Famous for his equation and the cat analogy

Question 14

James Chadwick

Answer 14

• Discovered neutrons in 1932 which led to discovery of fission and the atomic bomb
• Helped with the development of the nuclear model

Question 15

Louis de Broglie

Answer 15

• Wave-particle duality theory of light meaning electrons have properties of both waves and particles
• Created a new field of physics called wave mechanics

Question 16

Werner Heisenberg

Answer 16

• Founder of quantum mechanics
• Uncertainty principle
• Impossible to determine he position and the momentum of a particle at the same time
• “Cloud” model aka quantum mechanical model

Question 17

What are the postulate of the Atomic Theory?

1) Matter is composed of very tiny or microscopic particles called “Atom”.
2) Atom is an indivisible particle.
3) Atom can neither be created nor it is destroyed.
4) All of the above.

Answer 17

4) All of the above.