What do you know about What do you know about atoms?atoms?

• No books, no notes, no No books, no notes, no vocab., complete the vocab., complete the following: following: (this is not a test)(this is not a test)

– With the person next to you With the person next to you make a list of everything make a list of everything you know about atoms.you know about atoms.

– Draw a model of an atom.Draw a model of an atom.

Lets see your work...Lets see your work...

On the big screen!On the big screen!

Substances are Substances are made of ATOMSmade of ATOMS

3.13.1S. Martensen

Atomic TheoryAtomic Theory

• Atoms are the building blocks Atoms are the building blocks of all matter.of all matter.

• 2000 years after this was 2000 years after this was proposed we have evidence proposed we have evidence to support the idea but no to support the idea but no one has seen an atom.one has seen an atom.

Atomic ModelAtomic Model

• Old IdeaOld Idea • New IdeaNew Idea

See page 74 figures 1a and 1b

Law of Definite Law of Definite ProportionsProportions

• Any sample of the same Any sample of the same compound has the compound has the same elementssame elements in the in the same proportionssame proportions by mass. by mass.

• Example: NaCl (table salt)Example: NaCl (table salt)

– It is always 39.34% Na and 60.66% Cl by mass.It is always 39.34% Na and 60.66% Cl by mass.

– 1g of salt is 39.34% Na and 60.66% Cl.1g of salt is 39.34% Na and 60.66% Cl.

– 2000kg of salt is 39.34% Na and 60.66% Cl.2000kg of salt is 39.34% Na and 60.66% Cl.

Law of Conservation Law of Conservation of Massof Mass

• In a chemical reaction, the In a chemical reaction, the mass of the reactants = the mass of the reactants = the mass of the products.mass of the products.

See figure 3 page 76

DaltonDalton• Elements: One type of atomElements: One type of atom

• Compounds: 2 or more types of Compounds: 2 or more types of atomsatoms

• This was in 1808 and he was This was in 1808 and he was right!right!

Dalton’s 5 Principles of Atomic Dalton’s 5 Principles of Atomic TheoryTheory

1.1. All matter is composed of atoms.All matter is composed of atoms.

2.2. Atoms of an element are identical.Atoms of an element are identical.

3.3. Atoms of different elements differ Atoms of different elements differ physically and chemically.physically and chemically.

4.4. Atoms of different elements combine in Atoms of different elements combine in whole number ratios to form compounds.whole number ratios to form compounds.

5.5. In a chemical reaction, atoms are In a chemical reaction, atoms are combined, rearranged, separated but combined, rearranged, separated but NEVER created or destroyed.NEVER created or destroyed.

#4 of Dalton’s Principles#4 of Dalton’s Principles

• HH22O means: 2 atoms of hydrogen and 1 O means: 2 atoms of hydrogen and 1 atom of oxygen combine to make 1 atom of oxygen combine to make 1 molecule of water. molecule of water. The ratio is 2:1.The ratio is 2:1.

• FeOFeO22: 1 atom of iron and 2 atoms of : 1 atom of iron and 2 atoms of oxygen combine to form 1 molecule of oxygen combine to form 1 molecule of iron oxide (rust). iron oxide (rust). The ratio is 1:2The ratio is 1:2

• NOTICE!!! There are no ½ or .5, etc… NOTICE!!! There are no ½ or .5, etc… Only whole number ratios.Only whole number ratios.

Practice:Practice:• List the elements and ratios for the compounds List the elements and ratios for the compounds

listed below. Do not try to name the listed below. Do not try to name the compound.compound.

1)1) CC66HH12120066

2)2) NHNH33

3)3) AlClAlCl33

4)4) HH22OO22

5)5) CC88HH1818

There is a periodic table in the back cover of

your textbook.

While I have your While I have your attention...attention...

Lets take a look at some of Lets take a look at some of the problems you were the problems you were having on ChemThink.having on ChemThink.

I took these screenshots I took these screenshots while you were working while you were working on the “quiz” for the on the “quiz” for the Particle Nature of Particle Nature of Matter.Matter.