1. Chemistry Sheds Light on Our Lives Unit 4 Atoms and Light
Glow in the Dark
Chemistry Sheds Light on Our Lives
Unit 4 Atoms and Light

2. Glow in the Dark 4.1 Development of Atomic Theory 4.2 Atomic Structure
4.3 Electron Structure
4.4 Periodic Table
4.5 Periodicity
4.6 Light
4.7 Light and Matter

3. 4.1 & 4.2 Atomic Theory and Atomic Structure
Objectives
Determine the location, charge, and relative mass of protons, neutrons, electrons.
Use symbols in writing isotope notation.
Identify isotopes using mass number and atomic number and determine the number of protons, neutrons and electrons.
Differentiate actual atomic mass of an element from the mass number of an isotope
Calculate average atomic mass from % abundances of an isotope

4. Atomic Structure Timeline
On Wednesday’s quiz, you will be expected to…
match scientists to their experiments and discoveries
place the models in chronological order

5. Democritus (400 B.C.)‏
Proposed that matter was composed of tiny indivisible particles
Not based on experimental data
Greek: atomos

6. Alchemy (next 2000 years)‏ Mixture of science and mysticism.
Lab procedures were developed, but alchemists did not perform controlled experiments like true scientists.

7. John Dalton (1807)‏ British Schoolteacher Billiard Ball Model
based his theory on others’ experimental data
Billiard Ball Model
atom is a uniform, solid sphere

8. John Dalton Dalton’s Atomic Theory
All matter is made of tiny particles “atoms”
Atoms cannot be created, divided, destroyed or changed into other types of atoms
Atoms of the same element have identical properties
Atoms of different elements have different properties
Atoms of different elements combine in whole-number ratios to form compounds
Chemical changes join, separate or rearrange atoms in compounds

9. Henri Becquerel (1896)‏ Discovered radioactivity Three types:
spontaneous emission of radiation from the nucleus
Three types:
alpha () - positive
beta () - negative
gamma () - neutral

10. J. J. Thomson (1903)‏ Cathode Ray Tube Experiments
beam of negative particles
Discovered Electrons
negative particles within the atom
Plum-pudding Model

11. Cathode Ray Tubes
A cathode ray is a ray of light traveling in a vacuum (no other particles inside)
The ray travels from one metal plate to another as the plates are connected to electricity
Cathode ray
Metal plate (cathode) releases stream
Metal plate (anode) to which stream travels

12. Cathode Ray Tubes & Charge
In the late 1800’s, JJ Thomson put charged plates outside the tube
Negatively charged plate - +
Ray is deflected away from negative plate and towards positive plate
Positively charged plate
It made no difference what type of metal he used in the tube—all material produced this stream that curved towards the positive charge

13. J. J. Thomson (1903)‏ Plum-pudding Model Chocolate Cookie Model
positive sphere (pudding) with negative electrons (plums) dispersed throughout
Chocolate Cookie Model
Dough is positive area and chips are negative electrons

14. Robert Millikan (1909) Discovered the charge of an electron
Balanced the downward gravitational force and the upward electrical and buoyant forces of charged oil droplets suspended between two metal plates.
Discovered the charge of an electron

15. Ernest Rutherford (1911)‏ Gold Foil Experiment Discovered the nucleus
dense, positive charge in the center of the atom
Nuclear Model

16. Ernest Rutherford (1911)‏

17. Ernest Rutherford (1911)‏ Nuclear Model dense, positive nucleus
Mainly empty space filled with electrons

18. Niels Bohr (1913)‏ Bright-Line Spectrum Energy Levels Planetary Model
tried to explain presence of specific colors in hydrogen’s spectrum
Energy Levels
He stated that electrons can only exist in specific energy states
Planetary Model

19. Niels Bohr (1913)‏ Bright-line spectrum Planetary Model
electrons move in circular orbits within specific energy levels

20. Erwin Schrödinger (1926)‏ Quantum mechanics Electron cloud model
electrons can only exist in specified energy areas
Electron cloud model
orbital: region around the nucleus where e- are likely to be found

21. James Chadwick (1932)‏ Discovered neutrons Joliot-Curie Experiments
neutral particles in the nucleus of an atom
Joliot-Curie Experiments
based his theory on their experimental evidence

22. revision of Rutherford’s Nuclear Model
James Chadwick (1932)‏
Neutron Model
revision of Rutherford’s Nuclear Model

23. Make a chart like the one below and fill it in to help you study for your quiz.
Scientist
Experiment
Discoveries
New model described
New model drawing
Dalton (1809)
Other’s data
6 postulates
(two were later proven incorrect)
Billiard Ball Model
Thomson (1903)
Millikan (1909)
Rutherford (1911)
Bohr (1913)
Bright-Line Spectrum
Schrödinger (1926)
N/A
Chadwick (1932)