10F Science

10F Science

Atoms and Elements: Models of Matter I

Vocabulary & People alchemy element atomsubatomic electron neutralproton neutronDemocritus DaltonThomson Rutherford

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.

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?

• 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”

Goals1. 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

• 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.

Wrote the *FIRST Atomic Theory:

1. All matter made of indivisible particles – atom2. Atoms of elements are unique: differing by mass3. Compounds are combinations of elements4. Atoms cannot be created or destroyed (Law of Conservation of Matter)

*Does this list sound familiar?

2. Dalton (1800)

Dalton’s “atoms”

Experiments proved 1st 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

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!

Hypothesis:Atoms composed of empty space with a dense (+) nucleus and tiny (-) electrons flying around.

2nd subatomic particle: Proton: positive electric charge, found in nucleus.

Rutherford’s “atoms”

Rutherford’s model is called the “bee hive”

model

3rd subatomic particle: • Discovered in 1932Neutron: found in nucleus, NO charge, the size of protons

The Atom3 subatomic particles:Dense nucleus: Neutron – no charge Proton – (+) charge

Electrons – (-) charge, orbits nucleus

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

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 atomsubatomic electron neutralproton neutronDemocritus DaltonThomson Rutherford