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ATOMS (notes) • What are atoms? Atoms are the smallest unit of an element; it is the building block of matter. Atoms have the chemical properties of that element. Let’s review: What is a chemical property of iron? (Iron is an element) - It can rust when it comes in contact with oxygen and water According to our definition, this means that an atom of iron has the ability to rust. Today, we know atoms exist… Today we can put anything under a microscope and see that they are made up of atoms…so we have evidence that atoms exist!!!! Salt under a microscope!!!! Limestone!!! Limestone under a microscope!!!! Diamond!!! Diamond under a microscope!!!! How did scientists know atoms existed back in the day when they did not have such technology and couldn’t see them? 1. Observed 2. Scientific Question – when you keep cutting a piece of cheese in half forever, what will you be left with? 3. Hypothesis – If cheese is cut forever, then smaller pieces of cheese will be created until cheese can’t be cut anymore . 5. Conduct an experiment 6. Collect and analyze data 7. Draw a conclusion BUILD ON OTHER SCIENTISTS’ WORK DO NOW 1. Pick up SCIENCE FAIR 2013 handout from DO NOW FOLDER. Answer the following questions in you notebook. 1. Summarize Thomson’s experiment. What did he discover? 2. Summarize Rutherford’s experiment. What did he discover? 3 THING THAT NEED TO BE OUT ON YOUR DESK ARE… HOMEWORK IS DUE TODAY!! Make sure to leave it in your period’s TURN IN box before you leave class. SCIENTISTS IN HISTORY: ATOMIC THEORY VOCAB: ATOMIC THEORY: an idea of what the atom is, what it is made of, and what it looks like. What does “idea” mean to you? Is an idea based on evidence? John Dalton • 1766 • Dalton’s Atomic Theory: 1. All elements are made up of atoms 2. Atoms of one elements are the same; atoms of different elements are different 3. Compounds are made up of atom of different elements 4. Ratio of elements in a compound are the same Dalton did experiments and had evidence: splitting water molecules J. J. Thomson Cathode Ray Tube Experiment J.J. Thomson • 1897 • This was the first evidence that atoms are made of smaller, negatively charged particles. He called these particles electrons. • Thomson knew that an atom was neutral (has no charge). How can atom contain negative particles and still be neutral? - There must be positive charges to cancel out the negative charge How did J.J. Thomson disprove Dalton’s atomic theory? • Disproved Dalton theory by showing atom can be divided into positive and negative particles. • Atomic theory: The negatively charged particles are evenly scattered or spread in positively charged atom. • Name of atomic theory model: Plum pudding model Ernest Rutherford Gold Foil Experiment Ernest Rutherford • 1909 How can positive charge repel? - When positive charge comes near another positive charge • Evidence: The positive light is hitting something dense and positive within the atom for the light to be repelled and bounced back • Rutherford’s atomic model: all of an atoms positive charge is concentrated at its center or the nucleus. -Positively charged particle in that atom became known as protons. • Atomic theory: Electrons are found around the nucleus that contains the protons. Between the electrons and the nucleus was empty space. • Atomic model name: Solar system model SCIENTISTS IN HISTORY: ATOMIC THEORY You will be in divided into 6 groups and will be assigned a scientist who contributed to the atomic theory YOUR GOAL: As a group, you’ll use your notes to pull out important information about the scientist and fill out the table on the handout. After you get the table checked off by me, you and your group will make a poster for your scientist to go in a science magazine to headline his discovery and contribution. POSTER CONTEST? GALLERY WALK Now that everybody’s posters are up, as a group you are going to stop by the other posters and get the same information for the other scientists. MUST TURN IN: you groups’ table that I check of on as well as completed table for all scientists.