10F Science

1. Atoms and Elements: Models of Matter I 10F Science

2. 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. Vocabulary & People alchemy element atom subatomic electron neutral proton neutron Democritus Dalton Thomson Rutherford

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

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

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

6. 2. Dalton (1800) Wrote the *FIRST Atomic Theory: • All matter made of indivisibleparticles – atom • Atoms of elements are unique: differing by mass • Compounds are combinations of elements • Atoms cannotbe created or destroyed (Law of Conservation of Matter) *Does this list sound familiar? Dalton’s “atoms”

7. 3. Thomson (1890) Experiments proved1stsubatomicparticle: Electrons: small, negative electric charges. Electrons are sosmall they are considered “mass-less” Hypothesis: Atoms are sphereswith (+) charges mixed with the same number of (-) electrons. • Overallatom is neutral Thomson’s model is called the “plum-pudding” model Thomson’s “atoms”

8. 4. Rutherford (1910) “Gold Foil” experimentdiscoveredatomic nucleus Rutherford basically shot small “bullets” at a sheet of gold expecting them to strike the wall of atoms and bounce back – most went straight through!

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

10. 3rdsubatomic 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. 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 Dalton Pool ball model • Elements have unique atoms
 • Compounds are linked elements
 • Cannot create or destroy atoms

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 alchemy element atom subatomic electron neutral proton neutron Democritus Dalton Thomson Rutherford