1. 10F Science

2. Vocabulary & People alchemyelementatom subatomicelectronneutral protonneutron DemocritusDalton ThomsonRutherford S1-2-01 Describe how historical ideas and models furthered our understanding of the nature of matter. S1-2-02 Investigate the historical progression of the atomic model.

3. Early Philosophers (not Scientists) 1. Democritus (400 BCE) 2. Aristotle (350 BCE) Hypothesis: Matter is tiny particles in constant motion – atomos Cannot be broken apart – solid Eternal - can’t be created or destroyed “atomos” – means indivisible Hypothesis: Matter is made of 4 elements Earth, Air, Fire, Water Aristotle was the student of the famous Plato, Democritus was not…who did the world believe?

4. First recorded use of the “scientific method” (observation, experimentation, measurement and classification) Concerned with metallurgy (study of metals) 3. Alchemy (500 – 1600 CE) Alchemists are consider the first “scientists” Goals 1.Turn common metals into gold 2.Find the solution to eternal life Alchemists believed the “key” to both goals was the same and called it the Philosopher’s Stone

5. Experimented to prove Aristotle’s water and air were mixtures of elements Experimented to prove elements can’t be created or destroyed 1. Lavoisier (1750) Early Scientists At the time there were only 17 “substances” Defined element: Pure substance that cannot be broken down into simpler parts.

6. Wrote the *FIRST Atomic Theory: 1. All matter made of indivisible particles – atom 2. Atoms of elements are unique: differing by mass 3. Compounds are combinations of elements 4. Atoms cannot be created or destroyed (Law of Conservation of Matter) *Does this list sound familiar? 2. Dalton (1800) Dalton’s “atoms”

7. Experiments proved 1 st subatomic particle: Electrons: small, negative electric charges. Thomson’s “atoms” 3. Thomson (1890) Electrons are so small they are considered “mass-less” Hypothesis: Atoms are spheres with (+) charges mixed with the same number of (-) electrons. Overall atom is neutral Thomson’s model is called the “plum-pudding” model

8. 4. Rutherford (1910) “Gold Foil” experiment discovered atomic nucleus Rutherford basically shot tiny “bullets” at a sheet of gold expecting them to slice right through the thin sheet – but some bounced straight back!

9. Hypothesis: Atoms composed of empty space with a dense (+) nucleus and tiny (-) electrons flying around. 2 nd subatomic particle: Proton: positive electric charge, found in nucleus. Rutherford’s “atoms” Rutherford’s model is called the “bee hive” model

10. 3 rd subatomic particle: Discovered in 1932 Neutron: found in nucleus, NO charge, the size of protons The Atom 3 subatomic particles: Dense nucleus: Neutron – no charge Proton – (+) charge Electrons – (-) charge, orbits nucleus

11. Dalton Pool ball model -Elements have unique atoms -Compounds are linked elements -Cannot create or destroy atoms Thomson Plum pudding model -Experiments found electrons -Atoms are neutral Rutherford Beehive model -Experiments found nucleus and protons -(Neutral neutrons discovered later) -Atoms are mostly empty space

12. CAN YOU ANSWER THESE QUESTIONS? S1-2-01: How did each person contribute to the understanding of matter? S1-2-02: What is the basic subatomic structure of an atom? Vocabulary & People alchemyelementatom subatomicelectronneutral protonneutron DemocritusDalton ThomsonRutherford