History of the Atom Activity

Warm - Up

• Make a square using the puzzle pieces on your desk

• You discover a missing piece to the puzzle. Work by yourself to fit the piece in and make a new square.

• How does this relate to making a discovery in science?

Objective

Homework

• Review History of the Atom PowerPoint on my website, fill in gaps of information

Agenda

• Warm – Up• Review Mole HW• History of the Atom Research• Construction of Timeline• Gallery Walk• Exit Ticket

• Working in groups of 4 (6 groups)– 1 computer per group– Class set of textbooks

• Each person will be assigned four scientists to research

• Research the scientist• Complete chart• Share information with the group• Construct a timeline of for the history of the atom

Project Format

• Name of Scientist• Their Accomplishment– Regarding the atom– Development of the atom

• Date of discovery• Picture of the experiment (if there is an experiment) – – Explain what they found in their experiment

• Picture of the model of the atom constructed (if there is a picture available)– What is the model of the atom showing?

What to Research

History of the Atom Notes

Democritus (400 BC)

• All matter is composed of tiny, indivisible parts called atoms

• Said they could not be divided any further

John Dalton (1803)

• Dalton’s Atomic Theory• All matter is composed of tiny indivisible parts called

atoms (they can be broken down further, although properties will not be retained)

• Atoms of the same element are exactly alike, atoms of different elements are different (not all atoms of the same element have the same mass – isotopes)

John Dalton (1803)

• Atoms can combine in simple ratios to form compounds

• Atoms are neither created nor destroyed - Atoms cannot be destroyed, they simply rearrange in a chemical change, therefore the total amount of atoms remains the same

John Dalton (1800’s)

J.J. Thomson (1897)

• Plum Pudding Model of the Atom• Discovered the electron• Worked with Cathode Ray Tubes• Discovered particles with a negative charge,

electrons – knew they were negative charges by the deflection of the beam from a magnet

• “Pudding” is positive

J.J. Thomson (1897)

J.J. Thomson (1897)

• Discovered that the beam going between the anode and cathode could be deflected by bringing a magnet close to the cathode ray tube. The deflection that Thomson observed showed that the beam must have been made up of negatively charged particles

Ernest Rutherford (1911)

• Gold Foil Experiment – worked with alpha particles• Discovered that atoms have a nucleus

Ernest Rutherford (1911)

Niels Bohr (1914)

• Electrons occupy different fields or energy levels• Based on the fact that atoms appeared to release

fixed amounts (quantized) of energy when exposed to heat

• When an electron is exposed to an energy source, it jumps to a higher energy level

• When the electron eventually falls back to its original position, energy is released

Niels Bohr (1914)

Niels Bohr (1914)

• Start of the Quantum Mechanical Model• Electrons are particles

Louis de Broglie (1924)

• Posed the question, “If light can be viewed in terms of both “wave” and “particle” properties, why can’t particles of matter, like electrons, be treated the same way?”

• His question/idea was later proved to be correct

Erwin Schrödinger (1926)

• Shows where electrons will probably be found by using the waves they leave behind

• Electrons are waves• Update to the Quantum Mechanical Model• Sometimes called the Electron Cloud Model

Erwin Schrödinger (1926)

Final Thought

• No model of the atom perfectly describes the behavior of subatomic particles

• It is difficult to come up with an analogy, because…

• The only thing that behaves like an atom is an atom

Exit Ticket