1 Chap 3: Atoms & the Periodic Table 2 Pre-Question #1 What is an atom? What is an atom? The basic...

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Chap 3: Atoms & the Chap 3: Atoms & the Periodic TablePeriodic Table

22

Pre-Question #1Pre-Question #1

What is an atom?What is an atom?The basic unit of matterThe basic unit of matter

What particles make up an atom?What particles make up an atom?Electrons, protons, and neutronsElectrons, protons, and neutrons

What are three laws that support the What are three laws that support the existence of atoms?existence of atoms?Law of definite proportionsLaw of definite proportionsLaw of conservation of massLaw of conservation of massLaw of multiple proportionsLaw of multiple proportions

33

Fold 2 pieces of paper as instructedFold 2 pieces of paper as instructedLabel the bottom Label the bottom

Law of definite proportionsLaw of definite proportionsLaw of conservation of massLaw of conservation of massLaw of multiple proportionLaw of multiple proportion

On top, write 3 bullets points each of what On top, write 3 bullets points each of what you learned from your readingyou learned from your reading

44

The Laws of Definite Law of definite The Laws of Definite Law of definite proportion- in samples of any chemical proportion- in samples of any chemical compound, the _____compound, the _____ of the _____of the ______ _ are always in the _____are always in the _____ proportionsproportions

ex: In water, there will always be 8 g O for 1 ex: In water, there will always be 8 g O for 1 g of H.g of H.

16 g O16 g O = = 8 g 8 g OO

2 g H2 g H 1 g 1 g HH

16 g16 g1 g1 g 1 g1 g

masses samples same

3-1. Foundations of Atomic Theory3-1. Foundations of Atomic Theory

55

Visual Concepts

Law of Definite ProportionsLaw of Definite Proportions

Chapter 3

66

The Law of Conservation of MassThe Law of Conservation of Mass

The mass of the reactant in a reaction The mass of the reactant in a reaction equals the mass of the productequals the mass of the product

77

Visual Concepts

Law of Conservation of MassLaw of Conservation of Mass

Chapter 3

88

Law of multiple proportion-Law of multiple proportion- whenever 2 whenever 2 elements form more than one compound, elements form more than one compound, the _____the ______ _ masses of one element that masses of one element that combine with the _____combine with the _____ mass of the other mass of the other element are in the ratio of small whole element are in the ratio of small whole numbersnumbersEx: compare water and peroxide.Ex: compare water and peroxide.

Both molecules have the same number of H but Both molecules have the same number of H but different number of O, so the ratio is 1:2.different number of O, so the ratio is 1:2.

waterwater peroxideperoxide

different same

99

Visual Concepts

Law of Multiple ProportionsLaw of Multiple Proportions

Chapter 3

1010

COCO

carbon monoxidecarbon monoxide

COCO22

carbon dioxidecarbon dioxide

1111

3-1. Development of Atomic Models3-1. Development of Atomic Models1.1. Greek model(300’s BC): Democritus Greek model(300’s BC): Democritus

believed matter cannot be broken believed matter cannot be broken foreverforever__________

2.2. Dalton’s atomic theory (pg 78):Dalton’s atomic theory (pg 78):a.a. Elements are composed of indivisible atomsElements are composed of indivisible atomsb.b. If same element, then same atomsIf same element, then same atomsc.c. Cannot be subdivided, created, or destroyedCannot be subdivided, created, or destroyedd.d. Can physically mix; can chemically combine Can physically mix; can chemically combine

in whole # ratioin whole # ratioe.e. Chem. Rxn occur when atoms separate, Chem. Rxn occur when atoms separate,

join, or rearrangejoin, or rearrange

atoms

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Chapter 1 Section ReviewChapter 1 Section Review

What is the atomic theory?What is the atomic theory?The theory that all matter is composed of The theory that all matter is composed of

atomsatomsWhat is a compound?What is a compound?

A compound is a substance made from two or A compound is a substance made from two or more kinds of atomsmore kinds of atoms

1313

State the law of definite proportions, State the law of definite proportions, conservation of mass and multiple conservation of mass and multiple proportionsproportionsLaw of definite proportionsLaw of definite proportions

Each sample of a given compound contains the Each sample of a given compound contains the same elements in the same proportions by mass same elements in the same proportions by mass regardless of the size or source of the sampleregardless of the size or source of the sample

Law of conservation of massLaw of conservation of massMass is neither created nor destroyed during a Mass is neither created nor destroyed during a

chemical reactionchemical reactionLaw of multiple proportionsLaw of multiple proportions

When the same elements combine to form When the same elements combine to form different compounds, they do so in mass ratios that different compounds, they do so in mass ratios that can be expressed by small, whole numbers.can be expressed by small, whole numbers.

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According to Dalton, what is the difference According to Dalton, what is the difference between an element and a compound?between an element and a compound?Element=composed of atoms, all have Element=composed of atoms, all have

identical propertiesidentical propertiesCompound= two or more kinds of atoms, with Compound= two or more kinds of atoms, with

different properties, combined in a simple, different properties, combined in a simple, whole number ratiowhole number ratio

Which of Dalton’s five principles still apply Which of Dalton’s five principles still apply to the structure of an atom?to the structure of an atom?Principles 3,4,5Principles 3,4,5

Principle 1= atoms can be divided into subatomic Principle 1= atoms can be divided into subatomic particlesparticles

Principle 2= isotopes exist with same atom, Principle 2= isotopes exist with same atom, different propertiesdifferent properties

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What law is described by the fact that What law is described by the fact that carbon dioxide consists of 27.3% carbon carbon dioxide consists of 27.3% carbon and 72.7% oxygen by mass?and 72.7% oxygen by mass?Law of definite proportionsLaw of definite proportions

What law is described by the fact that the What law is described by the fact that the ratio of the mass of oxygen in carbon ratio of the mass of oxygen in carbon dioxide to the mass of oxygen in carbon dioxide to the mass of oxygen in carbon monoxide is 2:1?monoxide is 2:1?Law of multiple proportionsLaw of multiple proportions

1616

Three compounds contain the element Three compounds contain the element sulfur and fluorine. How do the following sulfur and fluorine. How do the following data support the law of multiple data support the law of multiple proportions?proportions?Compound A: 1.188g F for 1.000g SCompound A: 1.188g F for 1.000g S

Compound B: 2.375g F for 1.000g SCompound B: 2.375g F for 1.000g S

Compound C: 3.563g F for 1.000g SCompound C: 3.563g F for 1.000g SThree compounds have masses of F Three compounds have masses of F

combined with 1.000g of S in a ratio of small, combined with 1.000g of S in a ratio of small, whole numbers. The ratio is 1.2.3whole numbers. The ratio is 1.2.3

Law of multiple proportionsLaw of multiple proportions

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Atoms and Periodic TableAtoms and Periodic Table

1818

3.3. Goldstein (1886): discovered______, positive Goldstein (1886): discovered______, positive particles, observed canal rays traveling particles, observed canal rays traveling opposite cathode raysopposite cathode rays

4.4. Thomson: discovered __ using a Thomson: discovered __ using a cathode-ray tubecathode-ray tube(1897); its mass is about (1897); its mass is about 1/2000 of a hydrogen atom(1900) Fig 3-4, 3-51/2000 of a hydrogen atom(1900) Fig 3-4, 3-5

5.5. Rutherford (1911): atom mostly empty space Rutherford (1911): atom mostly empty space with dense _______with dense _______

a.a. Fig 3-6: gold foil experiment Gold Foil ExperimentFig 3-6: gold foil experiment Gold Foil Experiment

6.6. Millikan(1916): e- carries ___ ___ of negative Millikan(1916): e- carries ___ ___ of negative charge and has a mass of ______ of a charge and has a mass of ______ of a hydrogen atomhydrogen atom

7.7. Chadwick (1932): discovered _______, no Chadwick (1932): discovered _______, no charge, same mass as a protoncharge, same mass as a proton

protons

e-

nucleus

one unit

1/1840

neutron

1919

Visual Concepts

Comparing Models of AtomsComparing Models of Atoms

Chapter 3

2020

Visual Concepts

Thompson’s Cathode Ray Thompson’s Cathode Ray Tube ExperimentTube Experiment

Chapter 3

2121

Visual Concepts

Rutherford’s Gold Foil Rutherford’s Gold Foil ExperimentExperiment

Chapter 3

2222

3-2 3-2 Subatomic ParticlesSubatomic Particles1.1. Nucleus:Nucleus:

a.a. 99.9% mass99.9% massb.b. IsotopeIsotope: same # of ______, different # of : same # of ______, different # of

_______; _______; - ex. 3 different isotopes of Ne: Ne-20, Ne-21, Ne-22- ex. 3 different isotopes of Ne: Ne-20, Ne-21, Ne-22

c.c. p+ = 1.673 x 10^-27 kgp+ = 1.673 x 10^-27 kgd.d. Atomic mass = ______ + _______Atomic mass = ______ + _______e.e. Atomic number = # of _______Atomic number = # of _______

2.2. Electron:Electron:a.a. Around the nucleus in a specific energy level Around the nucleus in a specific energy level

(Bohr)(Bohr)b.b. 9.109 x 10^-31 kg9.109 x 10^-31 kg

protons

neutrons

protons neutrons

protons

SymbolsSymbolsContain 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.

We can also put the mass number We can also put the mass number after the name of the elementafter the name of the element for for different isotopesdifferent isotopescarbon- 12carbon- 12, , carbon -14carbon -14

X Massnumber

Atomicnumber

2424

Tr 12A Table 3 p. 83 Properties of Subatomic Tr 12A Table 3 p. 83 Properties of Subatomic ParticlesParticles

Which is the smallest?

The Electron

Describe the information conveyed by each symbol.

The 1st symbol only shows the relative charge (use when that’s all you need). The 2nd also shows the mass number.

SUBATOMIC PARTICLE

2525

POSIT IVECHARG E

PROT ONS

NEUT RALCHARG E

NEUT RONS

NUCLEUS

NEG AT IVE CHARG E

ELECT RONS

AT OM

Most of the atom’s mass.

NUCLEUS ELECTRONS

PROTONS NEUTRONS NEGATIVE CHARGE

POSITIVE CHARGE

NEUTRAL CHARGE

ATOM

QUARKSAtomic Numberequals the # of...

equal in a neutral atom

Subatomic ParticlesSubatomic Particles

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B. Isotopes B. Isotopes

Atoms of the same element with different Atoms of the same element with different mass numbers.mass numbers.

C126

Mass #

Atomic #

Nuclear symbol:Nuclear symbol:

Hyphen notation: Hyphen notation: carbon-12carbon-12

Example ProblemExample Problem1. Give the Atomic number of the 1. Give the Atomic number of the

element shown.element shown.F

19 9

Ans. 9

22. Give the number of protons Give the number of protons and electrons for this and electrons for this element.element. Ans. 9 p+ and 9 e-

3. Give the mass number of the 3. Give the mass number of the element shown.element shown. Ans. 19

44. Give the number of Give the number of neutrons for this element.neutrons for this element.Ans. 10

# of n0 = mass # - atomic #

# of n0 = 19 – 9 = 10 n0

2828

Pre-Question #3Pre-Question #3how many protons, neutrons and how many protons, neutrons and

electrons are in an atom of sodium with electrons are in an atom of sodium with atomic number of 11?atomic number of 11? Atomic mass = 23 = # of protons + neutronAtomic mass = 23 = # of protons + neutronAtomic number = 11 = # of protons and electronsAtomic number = 11 = # of protons and electronsAtomic mass – atomic number = # of neutronAtomic mass – atomic number = # of neutronTherefore,Therefore,

11 proton, 11 electron11 proton, 11 electron12 neutron12 neutron

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B. IsotopesB. Isotopes

© Addison-Wesley Publishing Company, Inc.

3131

B. B. IsotopesIsotopes

Chlorine-37Chlorine-37

atomic #:atomic #:

mass #:mass #:

# of protons:# of protons:

# of electrons:# of electrons:

# of neutrons:# of neutrons:

1717

3737

1717

1717

2020

Cl3717

3232

Isotope Isotope

3333

Chapter 3.2 Section ReviewChapter 3.2 Section Review

Describe the difference between electrons, Describe the difference between electrons, protons and neutrons.protons and neutrons.ElectronElectron

the mass is much smaller than proton and neutron.the mass is much smaller than proton and neutron. -1 charge-1 chargeSurrounds the nucleusSurrounds the nucleus

Proton and NeutronProton and NeutronMake up atomic nucleusMake up atomic nucleus+1 and no charge, respectively +1 and no charge, respectively

3434

How are isotopes of the same element How are isotopes of the same element alike?alike?All isotopes of an element have the same All isotopes of an element have the same

number of protons and electronsnumber of protons and electronsWhat subatomic particle was discovered What subatomic particle was discovered

with the use of a cathode-ray tube?with the use of a cathode-ray tube?ElectronElectron

Write the symbol for element X, which has Write the symbol for element X, which has 22 electron22 electron

3535

Determine the number of electrons, protons and Determine the number of electrons, protons and neutrons for each of the followingneutrons for each of the following 80-Br80-Br

35 e, 35 p, 45 n35 e, 35 p, 45 n

106-Pd 106-Pd 46 e 46 p, 60 n46 e 46 p, 60 n

133-Cs133-Cs 55 e, 55 p, 78 n55 e, 55 p, 78 n

Calculate the atomic number and mass number Calculate the atomic number and mass number of an isotope that has 56 electrons and 82 of an isotope that has 56 electrons and 82 neutronsneutrons Atomic number = 56Atomic number = 56 Mass number 138Mass number 138

3636

Why must there be an attractive force to Why must there be an attractive force to explain the existence of stable nuclei?explain the existence of stable nuclei? If the repulsive force between positively If the repulsive force between positively

charged protons were the only force, a charged protons were the only force, a nucleus could not contain multiple protons.nucleus could not contain multiple protons.

Are hydrogen-3 and helium-3 isotopes of Are hydrogen-3 and helium-3 isotopes of the same element? Explain your answerthe same element? Explain your answerNo, they are isotopes of different elements, No, they are isotopes of different elements,

because they have different atomic numbers. because they have different atomic numbers. All isotopes of an element have the same All isotopes of an element have the same atomic number, not the same mass number. atomic number, not the same mass number.

3737

3-4 Atomic Mass3-4 Atomic Mass

Mass of atom at restMass of atom at restRefers to ONE atomRefers to ONE atomThe mass of an atom expressed in atomic The mass of an atom expressed in atomic

mass unitsmass units amu = atomic mass unitamu = atomic mass unit

the ratio of the average mass per atom of the the ratio of the average mass per atom of the element to 1/12 of the mass of 12C in its element to 1/12 of the mass of 12C in its nuclear and electronic ground state. nuclear and electronic ground state.

Hydrogen = 1amu, 1/12 of CHydrogen = 1amu, 1/12 of C

Atomic WeightAtomic Weight the abundance-weighted average mass of the abundance-weighted average mass of

an elementan element Based on abundance of each element in nature.Based on abundance of each element in nature. Each isotope has its own atomic mass, thus we Each isotope has its own atomic mass, thus we

determine the average from percent abundance.determine the average from percent abundance. Is not a whole number because it is an average. Is not a whole number because it is an average. are the decimal numbers on the periodic table.are the decimal numbers on the periodic table. Commonly reported in amu or grams/molCommonly reported in amu or grams/mol

3939

Calculating Atomic MassCalculating Atomic Mass

Carbon has two stable isotopesCarbon has two stable isotopesCarbon-12 has natural abundance of 98.89% Carbon-12 has natural abundance of 98.89%

and 12.000 amuand 12.000 amu

Carbon-13 has natural abundance of 1.11% Carbon-13 has natural abundance of 1.11% and 13.003 amuand 13.003 amu

Calculate the atomic massCalculate the atomic mass

4040

Carbon has two stable isotopesCarbon has two stable isotopesCarbon-12 has natural abundance of 98.89% and 12.000 amuCarbon-12 has natural abundance of 98.89% and 12.000 amuCarbon-13 has natural abundance of 1.11% and 13.003 amuCarbon-13 has natural abundance of 1.11% and 13.003 amu

Calculate the atomic massCalculate the atomic mass

1.1. GivensGivensCarbon-12 m=12.000 amu Abundance= 98.89%=0.9889Carbon-12 m=12.000 amu Abundance= 98.89%=0.9889Carbon-13 m = 13.0003 amu Abundance = 1.11%=0.0111 Carbon-13 m = 13.0003 amu Abundance = 1.11%=0.0111

2.2. Formula Formula atomic mass of carbon-avg atomic mass of carbon-avg = (mass C-12 x nat.abund) + (mass C-13 x nat.abund.)= (mass C-12 x nat.abund) + (mass C-13 x nat.abund.)

3.3. Plug in the #sPlug in the #s(12.000amu x 0.9889) + (13.003 amu x 0.0111)(12.000amu x 0.9889) + (13.003 amu x 0.0111)= 12.011 amu= 12.011 amu= 12.0 amu= 12.0 amu

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Chemical Quantities?Chemical Quantities?You can measure You can measure massmass, , volumevolume,or ,or

you can you can count particlescount particles..measure mass in measure mass in gramsgrams..measure volume in measure volume in litersliters..We count particles inWe count particles in MOLESMOLES.. Mole is abbreviated: molMole is abbreviated: mol

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What is the Mole? What is the Mole?

A counting number (like a dozen)A counting number (like a dozen)

6.02 x 106.02 x 102323 is called is called Avogadro’s Avogadro’s number.number.

1 mol = 1 mol = 6.02 6.02 10 102323 items items ( representative particles) ( representative particles)

A large amount!!!!A large amount!!!!

4343

1 mole of hockey pucks would 1 mole of hockey pucks would equal the mass of the moon!equal the mass of the moon!

1 mole of pennies would cover the 1 mole of pennies would cover the Earth 1/4 mile deep!Earth 1/4 mile deep!

1 mole of basketballs would fill a 1 mole of basketballs would fill a bag the size of the earth!bag the size of the earth!

4444

Molar Conversion ExamplesMolar Conversion ExamplesHow many atoms are in 2.50 How many atoms are in 2.50

moles of C? moles of C?

2.50 mol2.50 mol 6.02 6.02 10 102323 atoms atoms

1 mol1 mol

1.51 1.51 10 102424

=atoms C=atoms C

4545

1. 1. Calculate the #Calculate the # of atoms in 0.500 mol of Al of atoms in 0.500 mol of Al..1) Ans: 3.01 x 101) Ans: 3.01 x 1023 23 AlAl atomsatoms

0.500 mol Al x 0.500 mol Al x 6.02 x 106.02 x 102323 Al atoms Al atoms

1 mol Al1 mol Al

ExampleExample

2. 2. Calculate the #Calculate the # of moles of Na if a of moles of Na if a sample of Na contains 1.80 x 10sample of Na contains 1.80 x 102424 Na Na atoms.atoms.

2) Ans: 2) Ans: 2.99 mole Na 2.99 mole Na 1.8 x 101.8 x 102424 Na atoms x Na atoms x 1 mol Na 1 mol Na

6.02 x 106.02 x 102323 Na atoms Na atoms

4646

Molar Mass - Is the Mass (in Grams) of One Mole of a Substance

(often called molecular weight)

Molar massMolar mass or ___ or ___ is the generic term for the is the generic term for the mass of one mole of any substance (in grams) mass of one mole of any substance (in grams)

The same as: The same as:

1) gram molecular mass 1) gram molecular mass or ___ or ___ (molecules) (molecules)

2) gram formula mass 2) gram formula mass or ___ or ___ (ionic compounds) (ionic compounds)

3) gram atomic mass 3) gram atomic mass or ___ or ___ (elements) (elements)

MM

gmm

gfmgam

4747

Molar Mass of Elements Molar Mass of Elements = atomic mass = atomic mass (simply look at the periodic table)(simply look at the periodic table)

carboncarbon

aluminumaluminum

zinczinc

12.01 g/mol12.01 g/mol

26.98 g/mol26.98 g/mol

65.39 g/mol65.39 g/mol

4848

Mass to Mole ConversionMass to Mole ConversionHow many moles of carbon is 26 How many moles of carbon is 26

g of carbon? (find MM of C from g of carbon? (find MM of C from the periodic table)the periodic table)

26 g C26 g C 1 mol C1 mol C

12.01 g C12.01 g C= 2.2 mol C= 2.2 mol C

4949

1 mol Na1 mol Na

22.99 g Na22.99 g Na

Mass to Mole ConversionMass to Mole Conversion

How many moles is 5.69 g of Na? How many moles is 5.69 g of Na? Na = 22.99 g/molNa = 22.99 g/mol

5.69 g Na5.69 g Na = 0.247 mol Na= 0.247 mol Na

5050

Mole to Mass ConversionMole to Mass Conversion

How many grams are in 9.45 mol of How many grams are in 9.45 mol of nitrogen atoms?nitrogen atoms?

NN = 14.01 g/mol= 14.01 g/mol

9.45 mol 9.45 mol NN 14.01 g 14.01 g NN1 mol 1 mol NN

= = 132.39 =132 g 132.39 =132 g NN

5151

Molar ConversionsMolar Conversions

molar mass

(g/mol)

MASS

IN

GRAMS

MOLESNUMBER

OF

PARTICLES

6.02 1023

(particles/mol)

÷

X ÷

X

5252

Test Prep:Test Prep:

How many moles of carbon-12 are How many moles of carbon-12 are contained in exactly 6 grams of carbon-contained in exactly 6 grams of carbon-12?12?

1.1. 0.5mole0.5mole

2.2. 2.0moles2.0moles

3.3. 3.01 ×103.01 ×102323 moles moles

4.4. 6.02 ×106.02 ×102323 moles moles

5353

Test PrepTest Prep

How many atoms are contained in 97.6 g of How many atoms are contained in 97.6 g of platinum (Pt)?platinum (Pt)?

1.1. 5.16 × 105.16 × 103030

2.2. 3.01 × 103.01 × 102323

3.3. 1.20 × 101.20 × 102424

4.4. 1.10 × 101.10 × 102828

5454

What about compounds?What about compounds? Mass in grams of 1 mole equal the Mass in grams of 1 mole equal the

sum of the atomic massessum of the atomic massesWhat is the mass of one mole (molar What is the mass of one mole (molar

mass) of CHmass) of CH44??1 C = 12.01 g/mol1 C = 12.01 g/mol4 H x 1.01 g/mol = 4.04g/mol4 H x 1.01 g/mol = 4.04g/mol

1 mole CH1 mole CH44 = 12.01g/mol + 4.04 g/mol = 12.01g/mol + 4.04 g/mol

=16.05g/mol=16.05g/mol

5555

Molar Mass Example ProblemMolar Mass Example ProblemFind the molar mass of sodium bicarbonateFind the molar mass of sodium bicarbonate

NaHCONaHCO33

22.99g/mol + 1.01g/mol + 12.01g/mol + 22.99g/mol + 1.01g/mol + 12.01g/mol +

3(16.00 g/mol) 3(16.00 g/mol) = 84.01 g/mol= 84.01 g/mol

5656

Prozac, CProzac, C1717HH1818FF33NO, is a widely used NO, is a widely used

antidepressant that inhibits the uptake antidepressant that inhibits the uptake

of serotonin by the brain. It has a molar of serotonin by the brain. It has a molar

mass ofmass of

1) 40.0 g/mole1) 40.0 g/mole

2) 262 g/mole 2) 262 g/mole

3) 309 g/mole3) 309 g/mole

Example ProblemExample Problem

Solution: Solution: 17C 17C (12.0) (12.0) 18H 18H (1.0) (1.0) 3F 3F (19.0) (19.0) 1N 1N (14.0) (14.0) + 1 + 1 O (16.0)O (16.0) 309 g/mole309 g/mole

5757

1 mol NaOH1 mol NaOH

40.040.000 g NaOH g NaOH

Mass to Mole ConversionMass to Mole Conversion

How many moles is 5.69 g of NaOH? (Find How many moles is 5.69 g of NaOH? (Find MM of NaOH)MM of NaOH)Na = 22.99 g/molNa = 22.99 g/molO = 16.00 g/molO = 16.00 g/molH = H = 1.01 g/ mol 1.01 g/ mol

40.00 g/mol40.00 g/mol

5.69 g NaOH5.69 g NaOH = 0.142 mol NaOH= 0.142 mol NaOH

5858

Mole to Mass ConversionMole to Mass Conversion

How many grams are in 9.45 mol of How many grams are in 9.45 mol of dinitrogen trioxide?dinitrogen trioxide?

NN22OO33 = 2(14.01) + 3(16.00) = 76.02 g/mol = 2(14.01) + 3(16.00) = 76.02 g/mol

9.45 mol 9.45 mol NN22OO33 76.02 g 76.02 g NN22OO33

1 mol 1 mol NN22OO33

= = 718.2 =718 g 718.2 =718 g NN22OO33

5959

Representative particlesRepresentative particles

The smallest pieces of a substance.The smallest pieces of a substance.molecular compounds: molecule.molecular compounds: molecule.ionic compounds: formula unit.ionic compounds: formula unit.elements: atom.elements: atom.

6060

QuestionsQuestionsHow many atoms in the followingHow many atoms in the following

cmpdscmpds??CaCOCaCO33

55AlAl22(SO(SO44))33

1717

How many oxygen atoms in the aboveHow many oxygen atoms in the above cmpdscmpds??331212

6161

ContainsContains 6.02 x 106.02 x 102323 particles particles

1 mole C1 mole C = = 6.02 x 106.02 x 102323 C atoms C atoms

1 mole H1 mole H22O O == 6.02 x 10 6.02 x 102323 HH22O moleculesO molecules

1 mole NaCl 1 mole NaCl = = 6.02 x 106.02 x 102323 NaCl formula NaCl formula

units units

A Moles of ParticlesA Moles of Particles

6262

Another ExampleAnother Example

How many atoms of oxygen are there How many atoms of oxygen are there in 1.23 moles of COin 1.23 moles of CO22 ? ?

1.23 mol CO2

1 mol CO2

6.02 x 1023 molecules CO2

1 molecule CO2

2 atoms O

= 1.48 x 1024 atoms O

6363

More Molar Conversion More Molar Conversion ExamplesExamples

Find the mass of 2.1 Find the mass of 2.1 10 102424 molecules of NaHCOmolecules of NaHCO33. .

2.1 2.1 10 102424

moleculesmolecules 1 mol1 mol

6.02 6.02 10 102323

moleculesmolecules

= 290 g NaHCO= 290 g NaHCO33

84.01 g84.01 g

1 mol1 mol

6464

Practice ProblemsPractice Problems1. How many moles is 4.56 g of CO1. How many moles is 4.56 g of CO22??

2. How many grams is 9.87 moles of 2. How many grams is 9.87 moles of HH22O?O?

3. How many molecules is 6.8 g of 3. How many molecules is 6.8 g of CHCH44??

4. How much would 3.45 x 104. How much would 3.45 x 102222 atoms atoms of U weigh?of U weigh?

= .104 mol= .104 mol

= 178 g= 178 g

= 2.6 x 10= 2.6 x 102323 molec molec

= 13.6 g= 13.6 g

Copyright © by Holt, Rinehart and Winston. All rights reserved.

ResourcesChapter menu

2. Which of these is always equal to the number of protons in an atom?

F. the mass number

G. the number of isotopes

H. the number of neutrons

I. the number of electrons

Understanding Concepts

Chapter 3 Standardized Test Preparation



3. Which of these events occurs when an electron in an excited state returns to its ground state?

A. Light energy is emitted.

B. Energy is absorbed by the atom.

C. The atom undergoes spontaneous decay.

D. The electron configuration of the atom

changes.

Understanding Concepts




7. The model of the atom has changed over time because

F. earlier models were proven to be wrong.

G. electrons do not revolve around the nucleus.

H. as new properties of atoms were discovered, models had to be revised to account for those properties.

I. new particles were discovered, so the model had to be changed to explain how they could exist.

Reading Skills




8. Why do scientists need models as opposed to directly observing electrons?

A. Models can be changed. B. There is no technology that allows direct

observation of electrons. C. The charges on the electrons and protons

interfere with direct observation of the atom. D. Scientists cannot measure the speed of electrons with sufficient accuracy to determine which model is correct.

Reading Skills




9. What would cause scientists to change the current model of the atom?

Reading Skills




9. What would cause scientists to change the current model of the atom?

Answer: The current model of the atom would change if new data were found about atoms that could not be explained by the existing model. The new model would explain both the new data and all earlier observations.

Reading Skills


Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Vacuum tube

Metal Disks

7676

Some History on The Discovery of the

Atom Discovery of The Electron:

J.J. Thomson and the Cathode Ray Tube

(1897)

Calculated

e-/m

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


Voltage source

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Voltage source


By adding an electric fieldBy adding an electric field

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Voltage source

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

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Rutherford’s experimentRutherford’s experiment

Alpha particles - positively charged Alpha particles - positively charged particles- helium atoms minus electronsparticles- helium atoms minus electrons

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

When an alpha particle hits a fluorescent When an alpha particle hits a fluorescent screen, it glowsscreen, it glows

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Some History on The Discovery of the Atom

Rutherford’s Gold Foil Experiment and the Discovery of the Nucleus

Believed in Plum Pudding Model

Wanted to see How Large Atoms are

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 much.without changing direction very much.

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

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

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

positive piecepositive piece at at the center--the center--

the the nucleus.nucleus.Alpha particles Alpha particles

are deflected byare deflected by it, if they get closeit, if they get close enough.enough.

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Almost no deflection; few greatly deflectedAlmost no deflection; few greatly deflected

History of AtomHistory of Atom Democritus looked at Democritus looked at

beach (400 B.C.)beach (400 B.C.) Made of sandMade of sand Cut sand - smaller sandCut sand - smaller sand

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

1 Chap 3: Atoms & the Periodic Table 2 Pre-Question #1 What is an atom? What is an atom? The basic...

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Transcript of 1 Chap 3: Atoms & the Periodic Table 2 Pre-Question #1 What is an atom? What is an atom? The basic...