History of the Atom Activity

Informal assessment – monitoring group interactions and questions Objectives: Today I will be able to: Explore the nature of science by completing an activity Research a scientist to understand the history of the atom Informal assessment – monitoring group interactions and questions Formal assessment – analyzing student responses to the exit ticket Common Core Connection Build Strong Content Knowledge Value Evidence Come to understand other perspectives and cultures

Lesson Sequence Evaluate: Warm – Up Explore: History of the Atom Research Enage: Construction of Timeline Elaborate: Gallery Walk Evaluate: Exit Ticket

Warm - Up Complete the half sheet on atomic changes Use the word bank on the worksheet to complete the questions

Objective Today I will be able to: Explore the nature of science by researching the history of the atom Research a scientist to understand the history of the atom

Homework Study for the Atomic Structure Quiz on Friday October 10th (This Friday!)

Agenda Warm – Up History of the Atom Research Make a Flip Book Exit Ticket

History of the Atom Research Each member of the group will use textbooks and the computers to research their two assigned scientists

Analogies

Make an analogy Work with your group to create a real-life analogy for the Dalton, Thomson, Bohr and Schrodinger Models of the atom Look at Mr. Klotz’s example for guidance Share analogies with the class

History of the Atom Analogy Dalton’s Model Thomson’s Model

History of the Atom Analogy Bohr Model Sugar cookie with chocolate chips in rings around the outside Schrodinger Model Sugar cookie dipped in melted chocolate

The image of your analogy must be included in the flip book Make a flip book The image of your analogy must be included in the flip book

Flipbook Requirements For Dalton, Thompson, Rutherford, Bohr, Schrodinger Describe their model of the atom Draw a picture of their model of the atom Write and draw a picture of your analogy For Thompson and Rutherford – Describe the experiment For Dalton – Write the pieces of the atomic theory

History of the Atom Notes

Democritus (400 BC) Greek Philosopher All matter is composed of tiny, indivisible parts called “atomos” He said you cannot cut a piece of matter infinitely, but at some point you would get the smallest piece of matter possible. Said “atomos” could not be divided any further

John Dalton (1803) School Teacher Studied the ratios in which elements combine in a chemical reaction 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) 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) He created the “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 He also was able to estimate that the mass of the electron was equal to about 1/1800 of the mass of a hydrogen atom. His discovery of the electron won the Nobel Prize in 1906. He created the “plum pudding model” of the atom. “Pudding” is positive Electrons are embedded within the “pudding”

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 He showed that the production of the cathode ray was not dependent on the type of gas in the tube, or the type of metal used for the electrodes. He concluded that these particles were part of every atom.

Robert Millikan (1909) measured the charge of an electron using the oil drop experiment. x-rays gave the oil a negative electron 1.60x10^-19 coulomb is the charge of an electron using Thomson’s charge to mass ratio, he determined the mass of the electron is 9.11x10^-28g

Oil Drop Experiment

Ernest Rutherford (1911) Born in New Zealand 1871-1937 Tested Thomson’s theory of atomic structure with the “gold foil” experiment in 1910. Bombarded thin gold foil with a beam of ‘alpha’ particles. If the positive charge was evenly spread out, the beam should have easily passed through. All of the positive charge and most of the mass of an atom are concentrated in a small core, called the nucleus. Gold Foil Experiment (alpha scattering) he determined that an atom’s positive charge and most of its mass was concentrated in the core (most of the atom is empty space) he named the core “the nucleus”

Rutherford’s Gold Foil Experiment

Rutherford’s Model of the Atom Contained a positive nucleus Electrons were around the outside of the nucleus

Niels Bohr (1914) Start of the Quantum Mechanical Model Electrons are particles 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)

Werner Heisenberg Principle of uncertainty We cannot know both the location and the momentum of an electron The more we know about an electron’s position, the less uncertain we are

Erwin Schrödinger (1926) Based on Heisenberg's principle of uncertainty 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)

Exit Ticket Write two facts that you learned today about a scientist that another group member researched

Exit Ticket What does this activity teach us about the nature of scientific knowledge?