History of the Atom Activity

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/ Explain: History of the Atom Research Engage: 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

Warm - Up Using all of the pieces, except the piece with the x, arrange the pieces into the shape of a square. You discover a missing piece to the puzzle. Work by yourself to fit the new piece in and make a new square. How does this relate to making a discovery in science?

Warm Up How many water molecules are in 5.00 g of water (H 2 O)?

Warm - Up What mass of O 2 is present in 5.25 x molecules of O 2 ?

Warm - Up Complete the half-sheet! Review your Matter Quiz – Please let Ms. Ose know if you have any questions. – You will be handing it back in

Warm - Up Who is credited with the discovery of the electron? – What experiment helped with the discovery? What experiment helped determine the mass and charge of the electrons? – Whose experiment was it?

Objective Today I will be able to: – Explain the contributions of each scientist to the history of the atom – Apply knowledge of isotopes to a practice activity

Homework Study for Atomic Structure, Mole and History of Atom Quiz on Monday October 7

Agenda Warm – Up 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? Include APA citations for the sources used on your timeline What to Research

Each person must choose a scientist from each column to research DemocritusRobert MillikanNeils BohrJames Chadwick Louis de Broglie John DaltonJJ ThomsonErwin Schrodinger Michael Faraday Einstein Joseph Louis Proust Ernest Rutherford Marie CurieHenri Becquerel Geiger

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

Issac Newton (1704) Discovered that there are particles of light called “photons” Mechanics – a determinist universe that holds true for all solid bodies in motion

Joseph Proust (1799) He developed the Law of Definite Proportions – H 2 O always has 2 Hydrogen's and 1 Oxygen Discovered Oxygen Lead Dalton to his Atomic Theory

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) 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 He created the “plum pudding model” of the atom. – “Pudding” is positive – Electrons are embedded within the “pudding”

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.

Michael Faraday (1832) Focused his work on electromagnetism Discovered electrolysis – molecules can be split apart by using an electrical current

Henri Becquerel (1896) Worked with x – rays and photographic film Discovered some substances spontaneously decay, releasing energy

Marie Curie (1898) Worked with Uranium and Thorium Coined the term “radioactivity” Later discovered Polonium and Radium

Hans Geiger (1906) Developed a Geiger Counter Geiger Counters are used to detect radioactivity

Albert Einstein (1905) Wrote a paper convincing people that atoms did exist Put pollen in water – Observed the pollen “dancing” and being “bumped” around by water molecules

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 Tested Thomson’s theory of atomic structure with the “gold foil” experiment in 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)

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)

James Chadwick (1932) Neutrons- Discovered in 1932 (England ). He bombarded Beryllium with alpha particles. Neutrons were emitted and in turn ejected protons from paraffin.

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