Download II. Masses of Atoms

CH. 3 - ATOMIC STRUCTURE
The Atom: From Philosophical Idea to
Scientific Theory
OBJECTIVES
• EXPLAIN THE LAW OF CONSERVATION OF MASS, THE
LAW OF DEFINITE PROPORTIONS, AND THE LAW OF
MULTIPLE PROPORTIONS.
• SUMMARIZE THE FIVE ESSENTIAL POINTS OF
DALTON’S ATOMIC THEORY.
• EXPLAIN THE RELATIONSHIP BETWEEN DALTON’S
ATOMIC THEORY AND THE LAW OF CONSERVATION
OF MASS, THE LAW OF DEFINITE PROPORTIONS, AND
THE LAW OF MULTIPLE PROPORTIONS.
Chapter 3
FOUNDATIONS OF ATOMIC THEORY
• THE TRANSFORMATION OF A
SUBSTANCE OR SUBSTANCES
INTO ONE OR MORE NEW
SUBSTANCES IS KNOWN AS
A CHEMICAL REACTION.
• LAW OF CONSERVATION OF
MASS: MASS IS NEITHER
CREATED NOR DESTROYED
DURING ORDINARY
CHEMICAL REACTIONS OR
PHYSICAL CHANGES
Chapter 3
The Atom: From Philosophical Idea to
Scientific Theory
LAW OF CONSERVATION OF MASS
Click below to watch the Visual Concept.
Visual Concept
Chapter 3
FOUNDATIONS OF ATOMIC THEORY,
CONTINUED
• LAW OF MULTIPLE
PROPORTIONS: IF TWO OR
MORE DIFFERENT COMPOUNDS
ARE COMPOSED OF THE SAME
TWO ELEMENTS, THEN THE RATIO
OF THE MASSES OF THE SECOND
ELEMENT COMBINED WITH A
CERTAIN MASS OF THE FIRST
ELEMENT IS ALWAYS A RATIO OF
SMALL WHOLE NUMBERS
Chapter 3
LAW OF MULTIPLE PROPORTIONS
Click below to watch the Visual Concept.
Visual Concept
FOUNDATIONS OF ATOMIC THEORY,
CONTINUED
• LAW OF DEFINITE
PROPORTIONS: A CHEMICAL
COMPOUND CONTAINS THE
SAME ELEMENTS IN EXACTLY THE
SAME PROPORTIONS BY MASS
REGARDLESS OF THE SIZE OF
THE SAMPLE OR SOURCE OF THE
COMPOUND
Chapter 3
LAW OF DEFINITE PROPORTIONS
Click below to watch the Visual Concept.
Visual Concept
Chapter 3
DALTON’S ATOMIC THEORY
• ALL MATTER IS COMPOSED OF
EXTREMELY SMALL PARTICLES
CALLED ATOMS.
• ATOMS OF A GIVEN ELEMENT
ARE IDENTICAL IN SIZE, MASS,
AND OTHER PROPERTIES;
ATOMS OF DIFFERENT ELEMENTS
DIFFER IN SIZE, MASS, AND
OTHER PROPERTIES.
• ATOMS CANNOT BE
SUBDIVIDED, CREATED, OR
DESTROYED.
• ATOMS OF DIFFERENT ELEMENTS
COMBINE IN SIMPLE WHOLENUMBER RATIOS TO FORM
CHEMICAL COMPOUNDS.
• IN CHEMICAL REACTIONS,
ATOMS ARE COMBINED,
SEPARATED, OR REARRANGED.
Chapter 3
MODERN ATOMIC THEORY
• SOME IMPORTANT CONCEPTS REMAIN UNCHANGED.
• ALL MATTER IS COMPOSED OF ATOMS.
• ATOMS OF ANY ONE ELEMENT DIFFER IN PROPERTIES FROM
ATOMS OF ANOTHER ELEMENT.
• NOT ALL ASPECTS OF DALTON’S ATOMIC THEORY HAVE PROVEN TO
BE CORRECT. WE NOW KNOW THAT:
• ATOMS ARE DIVISIBLE INTO EVEN SMALLER PARTICLES.
• A GIVEN ELEMENT CAN HAVE ATOMS WITH DIFFERENT MASSES.
Chapter 3
THE STRUCTURE OF THE ATOM
• AN ATOM IS THE SMALLEST PARTICLE
OF AN ELEMENT THAT RETAINS THE
CHEMICAL PROPERTIES OF THAT
ELEMENT.
• THE NUCLEUS IS A VERY SMALL
REGION LOCATED AT THE CENTER OF
AN ATOM.
• THE NUCLEUS IS MADE UP OF AT LEAST
ONE POSITIVELY CHARGED PARTICLE
CALLED A PROTON AND USUALLY ONE
OR MORE NEUTRAL PARTICLES CALLED
NEUTRONS.
• THE NUCLEI OF ATOMS OF
DIFFERENT ELEMENTS DIFFER IN
THEIR NUMBER OF PROTONS
• THUS, THE NUMBER OF PROTONS
DETERMINES THAT ATOM’S
IDENTITY.
Chapter 3
FORCES IN THE NUCLEUS
• WHEN TWO PROTONS ARE EXTREMELY CLOSE TO EACH OTHER,
THERE IS A STRONG ATTRACTION BETWEEN THEM.
• A SIMILAR ATTRACTION EXISTS WHEN NEUTRONS ARE VERY CLOSE
TO EACH OTHER OR WHEN PROTONS AND NEUTRONS ARE VERY
CLOSE TOGETHER.
• THE SHORT-RANGE PROTON-NEUTRON, PROTON-PROTON, AND
NEUTRON-NEUTRON FORCES THAT HOLD THE NUCLEAR PARTICLES
TOGETHER ARE REFERRED TO AS NUCLEAR FORCES.
Chapter 3
THE STRUCTURE OF THE ATOM,
CONTINUED
• SURROUNDING THE NUCLEUS IS
A REGION OCCUPIED BY
NEGATIVELY CHARGED
PARTICLES CALLED ELECTRONS
• PROTONS, NEUTRONS, AND
ELECTRONS ARE OFTEN REFERRED • Atoms are electrically neutral
because they contain equal
TO AS SUBATOMIC PARTICLES.
numbers of protons and electrons.
• MOST OF THE ATOM IS EMPTY
Chapter 3
PROPERTIES OF SUBATOMIC PARTICLES
Chapter 3
THE SIZES OF ATOMS
• THE RADIUS OF AN ATOM IS THE DISTANCE FROM THE
CENTER OF THE NUCLEUS TO THE OUTER PORTION OF ITS
ELECTRON CLOUD.
• BECAUSE ATOMIC RADII ARE SO SMALL, THEY ARE
EXPRESSED USING A UNIT THAT IS MORE CONVENIENT
FOR THE SIZES OF ATOMS.
• THIS UNIT IS THE PICOMETER, PM.
• WHAT IS THE CHARGE OF A
NEUTRON?
• MOST OF AN ATOM IS
___________
• WHERE ARE ELECTRONS
FOUND?
• WHAT IS THE NUCLEUS OF AN
ATOM MADE UP OF?
• A MOLECULE OF CARBON MONOXIDE, CO,
HAS ONE ATOM OF OXYGEN WHILE A
MOLECULE OF CARBON DIOXIDE, CO2, HAS
TWO. IN A SAMPLE OF CO CONTAINING 1 G
OF CARBON, 1.33 G OF OXYGEN WILL
COMBINE WITH THE CARBON TO FORM THE
MOLECULE. WHAT IS THE MASS OF OXYGEN
IN A SAMPLE OF CO2 CONTAINING 1 G OF
CARBON?
A.1.33 G
C.2.66 G
B.3.0 G
D.0.0 G
Chapter 3
ATOMIC NUMBER
• ATOMS OF DIFFERENT ELEMENTS
HAVE DIFFERENT NUMBERS OF
PROTONS.
• ATOMS OF THE SAME ELEMENT
ALL HAVE THE SAME NUMBER OF
PROTONS.
• THE ATOMIC NUMBER OF AN
ELEMENT IS THE NUMBER OF
PROTONS OF EACH ATOM OF
THAT ELEMENT.
MASS NUMBER
• MASS # = PROTONS + NEUTRONS
 always a whole
number
 NOT on the
Periodic Table!
Publishing Company, Inc.
ISOTOPES
• ATOMS OF THE SAME ELEMENT WITH DIFFERENT
MASS NUMBERS.
 Nuclear symbol:
Mass #
Atomic #
 Hyphen notation: carbon-12
12
6
C
ISOTOPES
C. Johannesson
© Addison-Wesley Publishing Company, Inc.
ISOTOPES
• CHLORINE-37
• ATOMIC #:
17
• MASS #:
37
• # OF PROTONS:
17
• # OF ELECTRONS:
17
• # OF NEUTRONS:
20
37
17
Cl
AVERAGE ATOMIC MASS
• WEIGHTED AVERAGE OF ALL ISOTOPES
• ON THE PERIODIC TABLE
• ROUND TO 2 DECIMAL PLACES
Avg.
Atomic
Mass
(mass)(% )  (mass )(% )

100
AVERAGE ATOMIC MASS
• EX: CALCULATE THE AVG. ATOMIC MASS OF OXYGEN IF ITS ABUNDANCE IN
NATURE IS 99.76% 16O, 0.04% 17O, AND 0.20% 18O.
Avg.
(16)(99.76 )  (17)(0.04)  (18)(0.20)
 16.00
Atomic 
100
amu
Mass
AVERAGE ATOMIC MASS
• EX: FIND CHLORINE’S AVERAGE ATOMIC MASS IF APPROXIMATELY 8 OF EVERY 10
ATOMS ARE CHLORINE-35 AND 2 ARE CHLORINE-37.
Avg.
Atomic
Mass
(35)(8)  (37)(2)

 35.40 amu
10
CH 3- THE MOLE
COUNTING ATOMS
WHAT IS THE MOLE?
• A COUNTING NUMBER (LIKE A DOZEN) DESCRIBES
THE NUMBER OF PARTICLES
• AVOGADRO’S NUMBER (NA)
• 1 MOL = 6.02  1023 ITEMS
A
large amount!!!!
n
1 mole of hockey pucks would
equal the mass of the moon!
n
1 mole of basketballs would fill a
bag the size of the earth!
• 1 MOLE OF PENNIES WOULD COVER THE
EARTH 1/4 MILE DEEP!
Chapter 3
THE MOLE
Click below to watch the Visual Concept.
Visual Concept
MOLAR MASS
• MASS OF 1 MOLE OF AN ELEMENT OR
COMPOUND. - MOLAR MASS
• EQUAL TO ATOMIC MASS UNITS PER ATOM (AMU)
FOUND ON PERIODIC TABLE
• WRITTEN IN UNITS GRAMS PER MOLE (G/MOL)
MOLAR MASS EXAMPLES
• CARBON
12.01 g/mol
• ALUMINUM
26.98 g/mol
• ZINC
65.39 g/mol
MOLAR MASS EXAMPLES
• WATER
 H2O
 2(1.01) + 16.00 = 18.02 g/mol
• SODIUM CHLORIDE
 NaCl
 22.99 + 35.45 = 58.44 g/mol
MOLAR MASS EXAMPLES
• SODIUM BICARBONATE
 NaHCO3
 22.99 + 1.01 + 12.01 + 3(16.00)
= 84.01 g/mol
• SUCROSE
 C12H22O11
 12(12.01) + 22(1.01) + 11(16.00)
= 342.34 g/mol
Chapter 3
AVOGADRO’S NUMBER
Click below to watch the Visual Concept.
Visual Concept
MOLAR CONVERSIONS
molar
mass
6.02  1023
MASS
NUMBER
MOLES
IN
GRAMS
OF
Atoms/molecule
s
(g/mol)
(atoms/mol)
Chapter 3
SOLVING MOLE PROBLEMS
MOLAR CONVERSION EXAMPLES
• HOW MANY MOLES OF CARBON
ARE IN 26 G OF CARBON?
26 g C 1 mol C
12.01 g C
= 2.2 mol C
Chapter 3
MOLAR CONVERSION EXAMPLES
•WHAT IS THE MASS IN GRAMS OF 3.50
MOL OF THE ELEMENT COPPER, CU?
Chapter 3
•THE MOLAR MASS OF COPPER FROM THE
PERIODIC TABLE IS ROUNDED TO 63.55 G/MOL.
MOLAR CONVERSION EXAMPLES
• HOW MANY GRAMS OF CARBON
ARE IN 4.0 MOLES OF CARBON?
4.0 mol C 12.01 g C
= 48 g C
1 mol C
MOLAR CONVERSION EXAMPLES
• HOW MANY MOLECULES ARE IN
2.50 MOLES OF C12H22O11?
6.02  1023
2.50 mol molecules
1 mol
= 1.51  1024
molecules
C12H22O11
MOLAR CONVERSION EXAMPLES
• FIND THE MASS OF 2.1  1024
MOLECULES OF NAHCO3.
2.1  1024
84.01 g
molecules 1 mol
6.02  1023 1 mol
molecules
= 290 g NaHCO3