Chapter 4Chapter 4

The structure of the atomThe structure of the atom

EARLY IDEAS ABOUT EARLY IDEAS ABOUT MATTER…MATTER…

SECTION 4-1SECTION 4-1

The Atom…The Atom… Imagine you have a piece of aluminum Imagine you have a piece of aluminum

foil… and you cut it in half…foil… and you cut it in half…

Would you ever finish this task? Or could Would you ever finish this task? Or could you forever divide aluminum into smaller you forever divide aluminum into smaller and smaller pieces??and smaller pieces??

Early ideas about Early ideas about MatterMatter Ancient Greek PhilosophersAncient Greek Philosophers

– Democritus – “atomos” was Democritus – “atomos” was the smallest part of matterthe smallest part of matter

– NOT infinitely divisibleNOT infinitely divisible

Democritus vs. Democritus vs. AristotleAristotle Aristotle did NOT agree with Aristotle did NOT agree with

DemocritusDemocritus Matter is made up of fire, water, Matter is made up of fire, water,

air, and earth NOT small particlesair, and earth NOT small particles Because Aristotle was more Because Aristotle was more

famous, people believed himfamous, people believed him

WHO WOULD YOU WHO WOULD YOU BELIEVE? WHY?BELIEVE? WHY?

Asking people to believe either Asking people to believe either theory was like asking someone to theory was like asking someone to believe in Santa Clausbelieve in Santa Claus

Without scientific evidence… how Without scientific evidence… how can we know something exists can we know something exists without seeing it??without seeing it??

Take 2 minutes to write down what Take 2 minutes to write down what theory you would believe and why…theory you would believe and why…

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Alchemy for 2000 years

Aristotle believed that any substance could be transmuted (transformed) into any other substance simply by changing the relative proportions of the 4 basic qualities.

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Alchemy for 2000 years Alchemists were

searching for the evolution from ignorance to enlightenment. – elixir of life– philosopher’s stone– the aqua vitae– the panacea

John Dalton John Dalton (1766-1844)

He revived He revived Democritus’s Democritus’s ideasideas

Performed Performed SEVERAL chemical SEVERAL chemical reactions to reactions to develop his theorydevelop his theory

Dalton’s Atomic Dalton’s Atomic TheoryTheory

4 Major Ideas…4 Major Ideas… 1. Matter is composed of 1. Matter is composed of

small indivisible and small indivisible and indestructible particles called indestructible particles called ATOMSATOMS

2. Atoms of a given element 2. Atoms of a given element are identical in size, mass and are identical in size, mass and chemical propertychemical property

Dalton’s Atomic Dalton’s Atomic TheoryTheory 3. Different atoms combine in 3. Different atoms combine in

simple whole-number ratios simple whole-number ratios to form compounds.to form compounds.

4. In a chemical reaction 4. In a chemical reaction atoms are NEVER created or atoms are NEVER created or destroyed, destroyed, only rearrangedonly rearranged..

http://www.youtube.com/watch?v=HFF-2wyyTKc

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John Dalton (1766-1844)

He developed a system of symbols for each known element.

His symbols were round to model the tiny round atoms he was theorizing about

Today we have changed to the lettering system.

Law of Conservation of Law of Conservation of MassMass Dalton’s theory supports the Dalton’s theory supports the

law of conservation of mass.law of conservation of mass. Atoms cannot be created of Atoms cannot be created of

destroyed, so mass remains destroyed, so mass remains the same throughout the the same throughout the reaction.reaction.

ANSWER THE ANSWER THE FOLLOWING FOLLOWING

QUESTIONS…QUESTIONS… What does the law of What does the law of

conservation of mass state?conservation of mass state? How are the LAW OF How are the LAW OF

CONSERVATION OF MASS and the CONSERVATION OF MASS and the FOURTH idea of Dalton’s theory FOURTH idea of Dalton’s theory related?related?

HomeworkHomework

Read Section 4.1Read Section 4.1 Pg 105, # 1-5Pg 105, # 1-5