Atomic Theory

Question 1

Empedocles

Answer 1

• philosopher

- all substances are made up of Earth, air, fire, and water

Question 2

Democritus

Answer 2

• philosopher

- matter can be divided up into smaller pieces until a single indivisible particle is reached, called ATOM

Question 3

John Dalton-1803

BILLIARD BALL MODEL

Answer 3

• matter consists of small particles called atoms
• each element is unique and made up of own atom identical in size, mass and chemical and physical properties
• atoms of different elements have different properties
• atoms combine in whole number ratios (H2O)
• atoms can’t be created, destroyed or subdivided in a chemical change

Question 4

J.J. Thomson-1897

Answer 4

• used a cathode ray tube to discover the presence of electrons
• chocolate chip cookie model
• atom as a positively charged sphere with negative electrons sprinkled within it
• overall charge is neutral because the negatives balances the positives

Question 5

Ernest Rutherford-1911

Answer 5

• concluded three facts:
• the positive mass of an atom is located in the nucleus, the positive core
• electrons orbit around the nucleus very fast
• most of the atom is empty space
• Rutherford Model had a circular center called the nucleus where protons are found and a squiggly electron cloud around it
• Gold Foil Experiment to determine empty space

Question 6

James Chadwick-1932

Answer 6

-presence of neutrons which are neutrally charged

Question 7

Niels Bohr-1913

Answer 7

-electrons travel in energy levels
-they orbit the nucleus
-they can jump from one level to another
-they move fast
Line Spectra
-heat energy is added to an atom, resulting in it jumping from one level (the ground state) to another that is further from the nucleus (the excited state)
-once they fall back to a lower level, an emmission spectrum is seen