Prior Knowledge CheckPrior Knowledge Check Who first came up with the idea of the Who first came up with the idea of the

atom?atom? What particles are found in atoms?What particles are found in atoms? Where are these particles found?Where are these particles found?

Section 5.1Section 5.1AtomsAtoms

OBJECTIVES:OBJECTIVES:

–Summarize Dalton’s atomic Summarize Dalton’s atomic theory.theory.

–Describe the size of an atom.Describe the size of an atom.

History of the atomHistory of the atom Not the history of atom, but of the idea Not the history of atom, but of the idea

of the atom.of the atom. Original idea Ancient Greece (400 Original idea Ancient Greece (400

B.C.)B.C.) There were 2 different ideasThere were 2 different ideas Democritus and Leucippus- Greek Democritus and Leucippus- Greek

philosophersphilosophers..

History of AtomHistory of Atom Looked at beachLooked at beach Made of sandMade of sand Cut sand - smaller Cut sand - smaller

sandsand

Smallest Smallest possible piece?possible piece?Atomos - not to Atomos - not to be cutbe cut

Another GreekAnother Greek Aristotle - Famous philosopherAristotle - Famous philosopher All substances are made of 4 All substances are made of 4

elementselements Fire - HotFire - Hot Air - lightAir - light Earth - cool, heavyEarth - cool, heavy Water - wetWater - wet Blend these in different proportions to Blend these in different proportions to

get all substancesget all substances

Who Was Right?Who Was Right? Greeks did not experiment.Greeks did not experiment. Greeks settled disagreements by Greeks settled disagreements by

argument.argument. Aristotle was more famous.Aristotle was more famous. He won.He won. His ideas carried through middle His ideas carried through middle

ages.ages. Alchemists change lead to gold.Alchemists change lead to gold.

Who’s Next?Who’s Next? Late 1700’s - John Late 1700’s - John

Dalton- England.Dalton- England. Teacher- summarized Teacher- summarized

results of his experiments results of his experiments and those of others.and those of others.

Dalton’s Atomic TheoryDalton’s Atomic Theory Combined ideas of Combined ideas of

elements with that of elements with that of atoms.atoms.

Dalton’s Atomic TheoryDalton’s Atomic Theory All All mattermatter is made of tiny is made of tiny indivisibleindivisible

particles called atoms.particles called atoms. Atoms of the same element are Atoms of the same element are

identicalidentical, those of different elements , those of different elements are are differentdifferent..

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

Chemical reactions involve the Chemical reactions involve the rearrangementrearrangement of atoms. No new of atoms. No new atoms are created or destroyed.atoms are created or destroyed.

Just How Small Is an Atom?Just How Small Is an Atom? An An atomatom is the smallest particle of is the smallest particle of

an element that retains the an element that retains the properties of that elementproperties of that element

Atoms-very small: Fig. 5.2, p. 108Atoms-very small: Fig. 5.2, p. 108

–still observable with proper still observable with proper instruments: Fig. 5.3, page 108instruments: Fig. 5.3, page 108

Section 5.2Section 5.2Structure of the Nuclear AtomStructure of the Nuclear Atom

OBJECTIVES:OBJECTIVES:– Distinguish among protons, electrons, and Distinguish among protons, electrons, and

neutrons in terms of relative mass and charge.neutrons in terms of relative mass and charge.– Describe the structure of an atom, including the Describe the structure of an atom, including the

location of the protons, electrons, and neutrons location of the protons, electrons, and neutrons with respect to the nucleus.with respect to the nucleus.

– Describe the experiments of Thomson and Describe the experiments of Thomson and Rutherford.Rutherford.

Parts of AtomsParts of Atoms J. J. Thomson - J. J. Thomson -

English physicist. 1897English physicist. 1897 Made a piece of Made a piece of

equipment called a equipment called a cathode ray tube.cathode ray tube.

It is a vacuum tube - all It is a vacuum tube - all the air has been the air has been pumped out.pumped out.

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Vacuum tube

Metal Disks

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

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

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

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

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

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

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

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric fieldBy adding an electric field

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric fieldBy adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric fieldBy adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric fieldBy adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric fieldBy adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric fieldBy adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

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

+

-

Other particlesOther particles Proton - positively charged pieces Proton - positively charged pieces

1840 times heavier than the 1840 times heavier than the electron – by E. Goldstein (~1886)electron – by E. Goldstein (~1886)

Neutron - no charge but the same Neutron - no charge but the same mass as a proton – by J. Chadwick mass as a proton – by J. Chadwick (1932)(1932)

Where are the pieces?Where are the pieces?

Rutherford’s experimentRutherford’s experiment Ernest Rutherford -English Ernest Rutherford -English

physicist. (1910)physicist. (1910) Believed in the plum pudding Believed in the plum pudding

model of the atom (discussed model of the atom (discussed in Chapter 13).in Chapter 13).

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

Used radioactivity.Used radioactivity. Alpha particles - positively Alpha particles - positively

charged pieces- helium atoms charged pieces- helium atoms minus electronsminus electrons

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

Plum Pudding- Yuck!Plum Pudding- Yuck!

Rutherford’s experimentRutherford’s experiment When an alpha particle hits a When an alpha particle hits a

fluorescent screen, it glows.fluorescent screen, it glows. Here’s what it looked like (page 111)Here’s what it looked like (page 111)

Lead block

Uranium

Gold Foil

Fluorescent Screen

He ExpectedHe Expected The alpha particles to pass through The alpha particles to pass through

without changing direction very without changing direction very much.much.

Because…?Because…? ……the positive charges were the positive charges were

thought to be spread out evenly. thought to be spread out evenly. Alone they were not enough to stop Alone they were not enough to stop the alpha particles.the alpha particles.

What he expected

Because

He thought the mass was evenly distributed in the atom

Since he thought the mass was evenly distributed in the atom

What he got

How he explained it

+

Atom is mostly empty.Atom is mostly empty. Small dense,Small dense,

positive piecepositive piece at at center.center.

Alpha particles Alpha particles are deflected byare deflected by

it if they get close it if they get close enough. enough.

+

Density and the AtomDensity and the Atom Since most of the particles went Since most of the particles went

through, it was mostly empty space.through, it was mostly empty space. Because the pieces turned so much, Because the pieces turned so much,

the positive pieces were heavy.the positive pieces were heavy. Small volume, big mass, big density.Small volume, big mass, big density. This small dense positive area is the This small dense positive area is the

nucleus.nucleus.

Subatomic particles – p.111Subatomic particles – p.111

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

Section 5.3Section 5.3Distinguishing Between AtomsDistinguishing Between Atoms

OBJECTIVES:OBJECTIVES:

–Explain how the atomic number Explain how the atomic number identifies an element.identifies an element.

Section 5.3Section 5.3Distinguishing Between AtomsDistinguishing Between Atoms

OBJECTIVES:OBJECTIVES:

–Use the atomic number and mass Use the atomic number and mass number of an element to find the number of an element to find the numbers of protons, electrons, numbers of protons, electrons, and neutrons.and neutrons.

Section 5.3Section 5.3Distinguishing Between AtomsDistinguishing Between Atoms

OBJECTIVES:OBJECTIVES:

–Explain how isotopes differ, and Explain how isotopes differ, and why the atomic masses of why the atomic masses of elements are not whole numbers.elements are not whole numbers.

Section 5.3Section 5.3Distinguishing Between AtomsDistinguishing Between Atoms

OBJECTIVES:OBJECTIVES:

–Calculate the average atomic Calculate the average atomic mass of an element from isotope mass of an element from isotope data.data.

Counting the PiecesCounting the Pieces Atomic Number Atomic Number = number of = number of

protons in the nucleusprotons in the nucleus # of protons determines kind of # of protons determines kind of

atom (since all protons are alike!)atom (since all protons are alike!) the same as the number of the same as the number of

electrons in the neutral atom.electrons in the neutral atom. Mass Number = Mass Number = the number of the number of

protons + neutrons.protons + neutrons. These account for most of massThese account for most of mass

SymbolsSymbols Contain the symbol of the element, Contain the symbol of the element,

the mass number and the atomic the mass number and the atomic number.number.

SymbolsSymbols Contain the symbol of the element, Contain the symbol of the element,

the mass number and the atomic the mass number and the atomic number.number.

X Massnumber

Atomicnumber

SymbolsSymbols Find the Find the

–number of protonsnumber of protons–number of number of

neutronsneutrons–number of number of

electronselectrons–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 an atomic if an element has an atomic

number of 34 and a mass number number of 34 and a mass number of 78 what is the of 78 what is the

–number of protonsnumber of protons

–number of neutronsnumber of neutrons

–number of electronsnumber of electrons

–Complete symbolComplete symbol

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

SymbolsSymbols if an element has 78 electrons and if an element has 78 electrons and

117 neutrons what is the 117 neutrons what is the

–Atomic numberAtomic number

–Mass numberMass number

–number of protonsnumber of protons

–Complete symbolComplete symbol

IsotopesIsotopes Dalton was wrong.Dalton was wrong. Atoms of the same element can Atoms of the same element can

have different numbers of have different numbers of neutronsneutrons.. different mass numbers.different mass numbers. called called isotopes.isotopes.

Naming IsotopesNaming Isotopes We can also put the mass number We can also put the mass number

after the name of the element.after the name of the element. carbon- 12carbon- 12 carbon -14carbon -14 uranium-235uranium-235

Atomic MassAtomic Mass How heavy is an atom of oxygen?How heavy is an atom of oxygen?

–There are different kinds of oxygen There are different kinds of oxygen atoms.atoms.

More concerned with More concerned with average average atomic atomic mass.mass.

Based on abundance of each element Based on abundance of each element in nature.in nature.

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

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-One twelfth the mass of a carbon-

12 atom. 12 atom. Each isotope has its own atomic Each isotope has its own atomic

mass, thus we determine the mass, thus we determine the average from percent abundance.average from percent abundance.

Calculating averagesCalculating averages Multiply the atomic mass of each Multiply the atomic mass of each

isotope by it’s abundance (expressed isotope by it’s abundance (expressed as a decimal), then add the results.as a decimal), then add the results.

Sample 5-5, p.120Sample 5-5, p.120

Atomic MassAtomic Mass Calculate the atomic mass of copper if Calculate the atomic mass of copper if

copper has two isotopes. 45.00% has a copper has two isotopes. 45.00% has a mass of 63 amu and the rest has a mass of 63 amu and the rest has a mass of 64 amu.mass of 64 amu.

Atomic MassAtomic Mass Magnesium has three isotopes. Magnesium has three isotopes.

79.10% magnesium 24, 10.00% 79.10% magnesium 24, 10.00% magnesium 25, and the rest magnesium 25, and the rest magnesium 26. What is the atomic magnesium 26. What is the atomic mass of magnesium?mass of magnesium?

If not told otherwise, the mass of the If not told otherwise, the mass of the isotope is the mass number in amuisotope is the mass number in amu

Atomic MassAtomic Mass Is not a whole number because it is Is not a whole number because it is

an average. an average. are the decimal numbers on the are the decimal numbers on the

periodic table.periodic table.

Section 5.4Section 5.4The Periodic Table: Organizing The Periodic Table: Organizing

the Elementsthe Elements OBJECTIVES:OBJECTIVES:

–Describe the origin of the periodic Describe the origin of the periodic table.table.

Section 5.4Section 5.4The Periodic Table: Organizing The Periodic Table: Organizing

the Elementsthe Elements OBJECTIVES:OBJECTIVES:

–Identify the position of groups, Identify the position of groups, periods, and the transition metals periods, and the transition metals in the periodic table.in the periodic table.

Development of the Periodic Development of the Periodic TableTable

mid-1800s, about 70 elementsmid-1800s, about 70 elements Dmitri Dmitri MendeleevMendeleev – Russian – Russian

chemistchemist Arranged elements in order of Arranged elements in order of

increasing atomic massincreasing atomic mass Thus, the first “Periodic Table” Thus, the first “Periodic Table”

MendeleevMendeleev

Left blanks for undiscovered Left blanks for undiscovered elementselements

When discovered, good predictionWhen discovered, good prediction Problems?Problems?

–Co and Ni; Ar and K; Te and ICo and Ni; Ar and K; Te and I

New wayNew way

Henry Henry MoseleyMoseley – British physicist – British physicist Arranged elements according to Arranged elements according to

increasing increasing atomic numberatomic number The arrangement todayThe arrangement today P.124 – long formP.124 – long form Symbol, atomic number & massSymbol, atomic number & mass

Periodic tablePeriodic table Horizontal rows = Horizontal rows = periodsperiods

–There are 7 periodsThere are 7 periods Periodic law: Periodic law: when the elements are when the elements are

arranged in order of atomic number, then there arranged in order of atomic number, then there are periodic repetition of physical and chemical are periodic repetition of physical and chemical propertiesproperties

Vertical column = Vertical column = groupgroup (or family) (or family)–Similar physical & chemical prop.Similar physical & chemical prop.– Identified by number & letterIdentified by number & letter

Areas of the periodic tableAreas of the periodic table

Group A elements = Group A elements = representative representative elementselements–Wide range of phys & chem prop.Wide range of phys & chem prop.–Metals, nonmetals, metalloids Metals, nonmetals, metalloids

(semimetals)(semimetals)–Very reactive, not reactiveVery reactive, not reactive–Solids, liquids and gasesSolids, liquids and gases

MetalsMetals

Group IA – Group IA – alkali metalsalkali metals Group 2A – Group 2A – alkaline earth metalsalkaline earth metals Transition metalsTransition metals and and InnerInner transition transition

metalsmetals – Group B – Group B MetalsMetals: electrical conductors, have luster, : electrical conductors, have luster,

ductile, malleableductile, malleable All metals are solids at room temperature, All metals are solids at room temperature,

except _____.except _____.

NonmetalsNonmetals

NonmetalsNonmetals: generally nonlustrous, : generally nonlustrous, poor conductors of electricitypoor conductors of electricity

–Some gases (O, N, Cl); some are Some gases (O, N, Cl); some are brittle solids (S); one is a fuming brittle solids (S); one is a fuming dark red liquid (Br)dark red liquid (Br)

Group 7A – Group 7A – halogenshalogens Group 0 – Group 0 – noble gasesnoble gases

Division between metal & Division between metal & nonmetalnonmetal

Heavy, stair-step lineHeavy, stair-step line MetalloidsMetalloids border the line border the line

–Properties intermediate between Properties intermediate between metals and nonmetalsmetals and nonmetals

Learn the general behavior and Learn the general behavior and trends of the elements, instead of trends of the elements, instead of memorizing each element property memorizing each element property