Atoms and their structureAtoms and their structure

History of the atomHistory of the atom

Original idea Ancient Greece (400 B.C..)Original idea Ancient Greece (400 B.C..)

Democritus Greek philosophers Democritus Greek philosophers

History of AtomHistory of AtomLooked at beachLooked at beach

Made of sandMade of sand

Smallest possible Smallest possible piece?piece?Atoms - not to be cutAtoms - not to be cut

Another GreekAnother Greek

Aristotle - Famous philosopherAristotle - Famous philosopher

All substances are made of 4 elementsAll substances are made of 4 elements

Fire - HotFire - Hot

Air - lightAir - light

Earth - cool, heavyEarth - cool, heavy

Water - wetWater - wet

Blend these in different proportions to get all Blend these in different proportions to get all substances substances

His ideas were mostly opinionHis ideas were mostly opinion

Examples?Examples?

Can you think of examples to prove Can you think of examples to prove invisible particles exist, even though we invisible particles exist, even though we can’t see them?can’t see them?

Who Was Right?Who Was Right?Greek society was slave basedGreek society was slave based

Beneath Famous to work with handsBeneath Famous to work with hands

did not experimentdid not experiment

Greeks settled disagreements by argumentGreeks settled disagreements by argument

Aristotle was more famousAristotle was more famous

He wonHe won

His ideas carried through middle ages.His ideas carried through middle ages.

Alchemists tried to change lead to goldAlchemists tried to change lead to gold

Who’s Next?Who’s Next?

1808- John Dalton- England1808- John Dalton- England

Teacher- summarized results of his Teacher- summarized results of his experiments and those of other’sexperiments and those of other’s

In Dalton’s Atomic TheoryIn Dalton’s Atomic Theory

Combined ideas of elements with that of Combined ideas of elements with that of atomsatoms

Dalton’s Atomic TheoryDalton’s Atomic Theory

1.1. All All mattermatter is made of tiny is made of tiny indivisibleindivisible particles particles (atoms)(atoms)

Dalton was wrong hereDalton was wrong here

2.2. Atoms of the same element are identicalAtoms of the same element are identical

3.3. Atoms can’t be subdivided, created, or Atoms can’t be subdivided, created, or destroyeddestroyed

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

5.5. Chemical reactions involve the Chemical reactions involve the rearrangement of atoms. rearrangement of atoms.

Fundamental Laws of ChemistryFundamental Laws of ChemistryDalton used “atoms” to explain the following laws:Dalton used “atoms” to explain the following laws:

1.1. Law of Conservation of MassLaw of Conservation of Mass• Number of reactants = number of productsNumber of reactants = number of products

2.2. Law of Definite ProportionsLaw of Definite Proportions– Compounds have a constant composition by massCompounds have a constant composition by mass– Every sample of water is made up of Every sample of water is made up of

2 H and 1 O; NaCl = 1 Na and 1 Cl2 H and 1 O; NaCl = 1 Na and 1 Cl– Does not matter how many crystals of NaCl you Does not matter how many crystals of NaCl you

havehave3.3. Law of Multiple ProportionsLaw of Multiple Proportions

– If two elements make up more than one If two elements make up more than one compound, then the ratio of the elements will compound, then the ratio of the elements will always be a whole number ratio.always be a whole number ratio.

– HH22O and HO and H22OO22 but not H but not H2.32.3OO0.70.7

AnalogyAnalogy

A bicycle has 2 wheels, a tricycle has A bicycle has 2 wheels, a tricycle has three wheels. It’s a 2:3 ratio, a small, three wheels. It’s a 2:3 ratio, a small, whole number ratiowhole number ratio

Now it’s your turn…Now it’s your turn…

Laws of Multiple and DefineteLaws of Multiple and Definete

Parts of AtomsParts of Atoms

J. J. Thomson - English physicist. 1897J. J. Thomson - English physicist. 1897

Made a piece of equipment called a Made a piece of equipment called a cathode ray tube.cathode ray tube.

It is a vacuum tube - all the air has been It is a vacuum tube - all the air has been pumped out, gas under low pressurepumped out, gas under low pressure

Why?Why?– Because without the pressure, the particles Because without the pressure, the particles

will flow easierwill flow easier

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-Vacuum tube

Metal Disks

AnodeCathode

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Passing an electric current makes a beam Passing an electric current makes a beam appear to move from the negative to the appear to move from the negative to the positive endpositive end

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Passing an electric current makes a ray Passing an electric current makes a ray appear to move from the negative to the appear to move from the negative to the positive endpositive end

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Passing an electric current makes a ray Passing an electric current makes a ray appear to move from the negative to the appear to move from the negative to the positive endpositive end

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Passing an electric current makes a ray Passing an electric current makes a ray appear to move from the negative to the appear to move from the negative to the positive endpositive end

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field By adding an electric field

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field By adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field By adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field By adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field By adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field By adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field he found that the By adding an electric field he found that the moving pieces were negative moving pieces were negative

+

-

Thomson`s ModelThomson`s Model

Found the electronFound the electron

Couldn’t find positive (for a Couldn’t find positive (for a while) while)

Said the atom was like plum Said the atom was like plum puddingpudding

Positive stuff, with the Positive stuff, with the electrons randomly electrons randomly surrounding itsurrounding it

Like watermelon, the seeds Like watermelon, the seeds are spread throughout and are spread throughout and do not contribute to the do not contribute to the mass of the fruitmass of the fruit

Millikan- 1909Millikan- 1909

Discovered the Discovered the charge on the charge on the electronelectronGave it a unit- Gave it a unit- Coulomb (C)Coulomb (C)11..602 x 10602 x 10-19-19 = q = q (q stands for (q stands for charge)charge)1/2000 mass of 1/2000 mass of hydrogenhydrogen

http://cwx.prenhall.com/petrucci/medialib/media_portfolio/02.html

Rutherford’s experimentRutherford’s experiment

Ernest Rutherford English physicist. (1910)Ernest Rutherford English physicist. (1910)

Believed in the plum pudding model of the Believed in the plum pudding model of the atom.atom.

Wanted to see how big they are Wanted to see how big they are

Used radioactivityUsed radioactivity

Alpha particles – He with pos. charge- given off Alpha particles – He with pos. charge- given off by uranium by uranium

Shot them at gold foil which can be made a Shot them at gold foil which can be made a few atoms thick few atoms thick

Lead block

Uranium

Gold Foil

Florescent Screen

He ExpectedHe Expected

The alpha particles to pass through The alpha particles to pass through without changing direction very muchwithout changing direction very much

Because the positive charges were spread Because the positive charges were spread out evenly. Alone they were not enough to out evenly. Alone they were not enough to stop the alpha particlesstop the alpha particles

What he expected

Because

Because, he thought the mass was evenly distributed in the atom

What he got

How he explained it

+Atom is mostly emptyAtom is mostly empty

Small dense,Small dense, positive piece positive piece at centerat center

Alpha particles are deflected by it if they Alpha particles are deflected by it if they get close enoughget close enough

““It was like shooting a bullet at a piece of It was like shooting a bullet at a piece of tissue paper and have the bullet reflect off tissue paper and have the bullet reflect off the paper back at you”the paper back at you”

+

What Did It Prove?What Did It Prove?

The atom has a nucleusThe atom has a nucleus

Small, dense bundle of positive chargeSmall, dense bundle of positive charge

Nucleus has a small volume compared to Nucleus has a small volume compared to the rest of the atomthe rest of the atom

Niels BohrNiels Bohr19131913

suggested that electrons in an atom suggested that electrons in an atom move in set paths around the nucleusmove in set paths around the nucleus

Much like planets orbit around the sunMuch like planets orbit around the sun

SummarizeSummarize

Create a table showing the experiment, Create a table showing the experiment, date and discovery from each of the date and discovery from each of the following:following:– Millikan, Dalton, Thomson, RutherfordMillikan, Dalton, Thomson, Rutherford

Modern ViewModern View

The atom is mostly The atom is mostly empty spaceempty space

Two regions:Two regions:– Nucleus- protons Nucleus- protons

and neutronsand neutrons– Electron cloud- Electron cloud-

region where you region where you might find an might find an electronelectron

Subatomic particlesSubatomic particles

Electron

Proton

Neutron

Name Symbol ChargeRelative mass

Actual mass (g)

e-

p+

n0

-1

+1

0

1/1840

1

1

9.11 x 10-28

1.67 x 10-24

1.67 x 10-24

Size of an atomSize of an atomAtoms are small.Atoms are small.

Protons and neutrons = nucleusProtons and neutrons = nucleus

Nucleus tiny compared to atomNucleus tiny compared to atom

If the atom was the size of a stadium, the If the atom was the size of a stadium, the nucleus would be the size of a marble.nucleus would be the size of a marble.

Radius of the nucleus near 10Radius of the nucleus near 10-15-15m.m.

Density near 10Density near 101414 g/cm g/cm

What charge does the nucleus contain?What charge does the nucleus contain?

Flinn Mapping the Atom activityFlinn Mapping the Atom activity

QuestionsQuestions

Three compounds containing O and k Three compounds containing O and k have 1.22g, 2.44g and 4.89g of K. Show have 1.22g, 2.44g and 4.89g of K. Show how this data supports the L.M.P.how this data supports the L.M.P.

Compare in terms of location, mass and Compare in terms of location, mass and charge- electrons, proton and neutroncharge- electrons, proton and neutron

If I change the number of protons in a If I change the number of protons in a substance, will it be the same substance?substance, will it be the same substance?

Counting the PiecesCounting the Pieces

Atomic Number Atomic Number = number of protons= number of protons

# of protons determines kind of atom# of protons determines kind of atom

Same as the number of electrons in the Same as the number of electrons in the neutral atomneutral atom

Atomic Mass = Atomic Mass = the number of protons + the number of protons + neutrons (AKA Mass Number)neutrons (AKA Mass Number)– All the things with massAll the things with mass

SymbolsSymbols

Contain the symbol of the element, the Contain the symbol of the element, the mass number and the atomic numbermass number and the atomic number

X Massnumber

Atomicnumber

SymbolsSymbols

Find the Find the – number of protonsnumber of protons– number of neutronsnumber of neutrons– number of electronsnumber of electrons– Atomic numberAtomic number– Mass NumberMass Number

F19 9

SymbolsSymbols Find the Find the

–number of protonsnumber of protons

–number of neutronsnumber of neutrons

–number of electronsnumber of electrons

–Atomic numberAtomic number

–Mass NumberMass Number

Br80 35

SymbolsSymbols if an element has 91 protons and if an element has 91 protons and

140 neutrons what is the 140 neutrons what is the

–Atomic numberAtomic number

–Mass numberMass number

–number of electronsnumber of electrons

–Complete symbolComplete symbol

IonsIons

Atoms that have a different number of Atoms that have a different number of electrons than they should haveelectrons than they should have– Gives the atom a chargeGives the atom a charge– Example: Carbon should have 6 electrons, Example: Carbon should have 6 electrons,

but Cbut C++ has 5 electrons. What charge does it has 5 electrons. What charge does it have?have?

IsotopesIsotopes

Dalton was wrong againDalton was wrong againAtoms of the same element Atoms of the same element can have different numbers can have different numbers of neutronsof neutrons– different mass numbersdifferent mass numbers– called isotopescalled isotopes

Example: Carbon-12; Example: Carbon-12; Carbon-13Carbon-13– Both have 6 protonsBoth have 6 protons– Carbon-12 has a relative Carbon-12 has a relative

mass of 12, Carbon-13 mass of 12, Carbon-13 has a relative mass of 13has a relative mass of 13

What’s Carbon-14?

Naming and Writing IsotopesNaming and Writing Isotopes

Put the mass number after the name of Put the mass number after the name of the elementthe element

carbon- 12carbon- 12

carbon -14carbon -14

uranium-235uranium-235

To write them, Put protons on bottom and To write them, Put protons on bottom and mass number on top:mass number on top:

C147

QuestionQuestion

How many p, e and n are in an atom of Cl-How many p, e and n are in an atom of Cl-37?37?

Mass number – atomic number = neutronsMass number – atomic number = neutrons

37-17 = 2037-17 = 20

17 p, 17 e, 20 n17 p, 17 e, 20 n

Practice- Pg 80Practice- Pg 80

Measuring Atomic MassMeasuring Atomic Mass

Unit is the Unit is the Atomic Mass Unit Atomic Mass Unit (amu)(amu)

One twelfth the mass of a carbon-12 atom. One twelfth the mass of a carbon-12 atom.

Each isotope has its own atomic mass we Each isotope has its own atomic mass we need the average from percent need the average from percent abundance.abundance.

Can a single atom have an AMU?Can a single atom have an AMU?

Atomic MassAtomic Mass

Is not a whole number because it is an Is not a whole number because it is an average. average. – The decimal numbers are on the periodic The decimal numbers are on the periodic

tabletable

It’s like calculating your grade- it’s made of It’s like calculating your grade- it’s made of percentages that are weightedpercentages that are weighted

Average Atomic MassAverage Atomic Mass

How heavy is an atom of oxygen?How heavy is an atom of oxygen?– There are different kinds of oxygen atoms.There are different kinds of oxygen atoms.

= abundance of each element in nature.= abundance of each element in nature.

Average of all the types of one elementAverage of all the types of one element

Don’t use grams because the numbers Don’t use grams because the numbers would be too smallwould be too small

Calculating averagesCalculating averages

You have five rocks, four with a mass of 50 You have five rocks, four with a mass of 50 g, and one with a mass of 60 g. What is the g, and one with a mass of 60 g. What is the average mass of the rocks?average mass of the rocks?

Total mass = 4 x 50 + 1 x 60 = 260 gTotal mass = 4 x 50 + 1 x 60 = 260 g

Average mass = 4 x 50 + 1 x 60 = 260 gAverage mass = 4 x 50 + 1 x 60 = 260 g 5 5 5 5

Average mass = 4 x 50 + 1 x 60 = 260 gAverage mass = 4 x 50 + 1 x 60 = 260 g 5 5 55 5 5

Calculating averagesCalculating averages

Average mass = 4 x 50 + 1 x 60 = 260 gAverage mass = 4 x 50 + 1 x 60 = 260 g 5 5 5 5

Average mass = .8 x 50 + .2 x 60Average mass = .8 x 50 + .2 x 60

80% of the rocks were 50 grams80% of the rocks were 50 grams

20% of the rocks were 60 grams20% of the rocks were 60 grams

Average = % as decimal x mass + Average = % as decimal x mass + % as decimal x mass + % as decimal x mass + % as decimal x mass + % as decimal x mass +

Atomic MassAtomic MassCalculate the atomic mass of copper if copper has two Calculate the atomic mass of copper if copper has two isotopes. 69.1% has a mass of 62.93 amu and the rest has isotopes. 69.1% has a mass of 62.93 amu and the rest has a mass of 64.93 amu.a mass of 64.93 amu.• (62.93*.691) + (64.93*?) = Answer(62.93*.691) + (64.93*?) = Answer• How do you find ??How do you find ??

• 100-69.1 = 30.9%100-69.1 = 30.9%

• (62.93*.691) + (64.93*.309) = 63.548(62.93*.691) + (64.93*.309) = 63.548• Check:Check:

• Periodic tablePeriodic table• Sig FigsSig Figs• LabelLabel

Atomic MassAtomic Mass

Magnesium has three isotopes. 78.99% Magnesium has three isotopes. 78.99% magnesium-24 with a mass of 23.9850 magnesium-24 with a mass of 23.9850 amu, 10.00% magnesium-25 with a mass of amu, 10.00% magnesium-25 with a mass of 24.9858 amu, and the rest magnesium-25 24.9858 amu, and the rest magnesium-25 with a mass of 25.9826 amu. What is the with a mass of 25.9826 amu. What is the atomic mass of magnesium?atomic mass of magnesium?

Moles and MassMoles and Mass

One mole of an element is equal to it’s One mole of an element is equal to it’s mass AMUmass AMU

Avegadro’s number is the number of Avegadro’s number is the number of particles in one mole of that substanceparticles in one mole of that substance

Example- You have one mole of Pt, what Example- You have one mole of Pt, what is it’s AMU? is it’s AMU?

Example- A mass of 2 g of Be contains Example- A mass of 2 g of Be contains how many moles?how many moles?

ReviewReview

How many p, e, n make up at atom of How many p, e, n make up at atom of carbon-13?carbon-13?

Write the symbol for oxygen-16Write the symbol for oxygen-16

What’s the difference between isotope and What’s the difference between isotope and ion? Create an pneumonic device for this ion? Create an pneumonic device for this difference.difference.

Science HumorScience Humor

A neutron walks into a bar. "I'd like a soda" he says. The A neutron walks into a bar. "I'd like a soda" he says. The bartender promptly serves up a soda. "How much will that bartender promptly serves up a soda. "How much will that be?" asks the neutron. "For you?" replies the bartender, "no be?" asks the neutron. "For you?" replies the bartender, "no charge" charge" Q: What happens when electrons lose their energy?Q: What happens when electrons lose their energy?A: They get Bohr'ed. A: They get Bohr'ed. Q: What did the thermometer say to the graduated cylinder?Q: What did the thermometer say to the graduated cylinder?A: "You may have graduated but I've got many degrees" A: "You may have graduated but I've got many degrees" A hydrogen atom came running into a police station asking for A hydrogen atom came running into a police station asking for help.... help.... Hydrogen atom: "Someone just stole my electron!"Hydrogen atom: "Someone just stole my electron!"Policeman: "Are you sure?"Policeman: "Are you sure?"Hydrogen atom: "Yes, I'm positive"Hydrogen atom: "Yes, I'm positive"Policeman: "Oh, I thought you were just being negative Policeman: "Oh, I thought you were just being negative again." again."