Chapter 3 - Atoms: the building blocks of matter

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Transcript Chapter 3 - Atoms: the building blocks of matter

Chapter 3 - Atoms: the building
blocks of matter
Taken from Modern Chemistry
written by Davis, Metcalfe, Williams
& Castka
Section 3.1 – The Atom: from philosophical idea to
scientific theory
HW – Notes on section 3.1 pgs 65-67
Objectives
Students will be able to :
• Explain the laws of
Conservation of mass
Definite proportion
Multiple proportion
• Summarize the 5 essential points of Dalton’s atomic
theory
• Explain the relationship between the 5 essential
points and the above mentioned laws
Section 3.1 – The Atom: from philosophical idea to
scientific theory
Foundations of Atomic Theory
As early as 400 B.C.E. particle theory of
matter was supported – the particle was
called an atom based on the Greek for
“indivisible”.
Supported by Democritus
Aristotle did not believe this theory
and his opinion lasted for 2 000 years. Felt
all matter was continuous.
Section 3.1 – The Atom: from philosophical idea to
scientific theory
Foundations of Atomic Theory (continued)
By 1700s accepted idea that an element could
not be broken down further. Back
The transformation of substance or substances
into one or more new substances was known as
a chemical reaction.
By the 1790s there was a new emphasis on
quantitative analysis of chemical reactions
Section 3.1 – The Atom: from philosophical idea to
scientific theory
Foundations of Atomic Theory (continued)
This work lead to the discovery of several
laws. . .
Law of Conservation of
matter which states that
mass is neither destroyed
or created during
ordinary chemical or
physical reactions.
Back
Antoine Lavoisier
Section 3.1 – The Atom: from philosophical idea to
scientific theory
Foundations of Atomic Theory (continued)
The law of definite
proportions, sometimes
called Proust's Law,
states that a chemical
compound always contains
exactly the same
proportion of elements by
mass.
Book example: salt is always 39.34% Na (sodium)
and 60.66% Cl (Chlorine) by mass
Joseph Proust
Section 3.1 – The Atom: from philosophical idea to
scientific theory
Foundations of Atomic Theory (continued)
The law of multiple
proportions, statement
that when two elements
combine with each other
to form more than one
compound, the weights of
one element that combine
with a fixed weight of
the other are in a ratio
of small whole numbers.
Back
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Section 3.1 – The Atom: from philosophical idea to
scientific theory
Dalton’s Atomic Theory
1.All matter is made of extremely small
particles called atoms. Relationship
2.All atoms of the same element are identical
in size, mass & other properties. Relationship
3.Atoms cannot be subdivided, created or
destroyed. Relationship
4.Atoms of different elements combine in
WHOLE-number ratios to form compounds.
5.In chemical reactions atoms are combined,
separated or rearranged. Relationship
Section 3.1 – The Atom: from philosophical idea to
scientific theory
Modern Atomic Theory
Dalton turned idea’s (of ancient Greeks) into
scientific theory
Today we know that atoms can be divided, but
the law of conservation of matter holds true
still.
Section 3.1 – The Atom: from philosophical idea to
scientific theory
Quiz Break
Section 3.2 – The Structure of the Atom
Objectives
HW – Notes on section 3.2 pgs 70-74
Students will be able to :
• Summarize the observed properties of cathode rays
that led to the discovery of the electron.
• Summarize the experiment carried out by
Rutherford and his co-workers that led to the
discovery of the nucleus.
• List the properties of protons, neutron and electrons
•Define atom.
Section 3.2 – The Structure of the Atom
Discovery of the Electron
1st discovery of a subatomic particle resulted from
investigations into the relationship between electricity
and matter.
Section 3.2 – The Structure of the Atom
Discovery of the Electron - Cathode Rays and Electrons
Hypothesized that the glow was caused by a stream of
particles which they called a cathode ray.
Tested and found that
1. An object placed between
the cathode ray and the
opposite end casts a
shadow.
2. A paddle wheel placed on
rails rolled toward the
anode from the cathode.
Section 3.2 – The Structure of the Atom
Discovery of the Electron - Cathode Rays and Electrons (continued)
This supported the idea of a cathode ray. . .
Further testing found that
1. Cathode rays were
deflected by a magnetic
field.
2. Deflected away from
negatively charged objects.
Thompson hypothesized that
the ray was a particle, a
negative one – later named
electrons.
Section 3.2 – The Structure of the Atom
Charge and Mass of the electrons
Thompson’s work showed that the electron has a
very large charge for its tiny mass
R. A. Millikan (right) showed the mass to be
9.109 x 10-31 kg
Section 3.2 – The Structure of the Atom
Charge and Mass of the electrons – (continued)
Based on that information two more inferences were
made about atomic structure.
1. Atoms are electrically neutral so there
must be positively charged particles to
balance out the negative electron.
2. Because electrons have so much less
mass than atoms, atoms must contain
other particles which account for most of
their mass.
Section 3.2 – The Structure of the Atom
Discovery of the Atomic Nucleus
Ernest Rutherford & associates bombarded a thin gold
foil with alpha particles (+ charge & 4 x mass of H atom)
Expected most particles to pass through with slight
deflection – shocked to find that 1 in 8 000 were
redirected back toward source.
Section 3.2 – The Structure of the Atom
Discovery of the Atomic Nucleus – (continued)
Rutherford reasoned that the bounce back was from a
densely packed bundle with a positively bundle he called
the nucleus.
If the nucleus were the size of a
marble the atom would be the size
of a football field
Section 3.2 – The Structure of the Atom
Composition of the Atomic Nucleus
Except for the simplest type of hydrogen all atomic nuclei
are made of two types of particles, protons and
neutrons.
Protons have a (+) charge which
balances out the charge of the electrons.
Mass = 1.673 x 10-27 kg
Neutrons have a no charge and a
mass = 1.675 x 10-27 kg
Section 3.2 – The Structure of the Atom
Composition of the Atomic Nucleus – (continued)
Nuclei of atoms of different elements differ in the # of
protons they contain and therefore in the amount of
positive charge.
Section 3.2 – The Structure of the Atom
Properties Summarized
Particle
Symbols
0
Relative
electric
charge
Mass
number
Relative
Mass (amu*)
Actual mass
(kg)
Electron
e-,-1 e
-1
0
0.000 5486
9.109 x 10-31
Proton
p+, 11 H
+1
1
1.007 276
1.673 x 10-27
Neutron
no, 0 n
0
1
1.008 665
1.675 x 10-27
1
* 1 amu (atomic mass unit) = 1.660 540 x 10-27 kg
Section 3.2 – The Structure of the Atom
Composition of the Atomic Nucleus - Forces in the Nucleus
Like forces generally repel one another however when
two protons are extremely close there is a strong
attractions
These short-range
proton-neutron,
proton-proton, and
neutron-neutron
forces hold the
particles together
and a referred to
as nuclear forces.
Section 3.2 – The Structure of the Atom
The sizes of Atoms
Atomic radii range from 40
to 270 pm (picometers)
Where as the nuclei of
atoms have a much smaller
radii
About 0.001 pm
Section 3.3(A) – Counting Atoms
Objectives
HW – Notes on section 3.3 pgs 75-80
Students will be able to :
• Explain what isotopes are.
• Define atomic number and mass number, and
describe how they apply to isotopes.
• Given the identity nuclide, determine its number of
protons, neutrons and electrons.
Section 3.3(A) – Counting Atoms
Atomic Number
The atomic number of an element is the
number of protons in the nucleus of
each atom of that element
Section 3.3(A) – Counting Atoms
Isotopes
Isotopes are atoms of the same element
that have different masses.
All hydrogen contain the same number
of protons but may contain different
number of neutrons.
Section 3.3(A) – Counting Atoms
Mass Number
The mass number is the total number of
protons and neutrons in the nucleus of
an isotope.
Mass
Number
1
2
3
Section 3.3(A) – Counting Atoms
Isotopes - pogil
Section 3.3(A) – Counting Atoms
Isotopes – Pennium Lab
Section 3.3(A) – Counting Atoms
Designating Isotopes
Nuclide is a general term for any
isotope of any element.
Nuclear
Symbol
a
b
S = element’s symbol
S
Bromine has
a = protons + neutrons
b = protons
80
Protons = ______
35
Neutrons = _______
Br
Electrons = ________
Practice
Practice Key
Section 3.3(A) – Counting Atoms
Relative Atomic Masses
The standard used by scientist to
govern units of atomic mass is the
carbon-12 nuclide. One atomic mass
unit , or amu is exactly 1/12th the
mass of a carbon-12 atom, or
1.660 540 x 10-27 kg
Although isotopes may have different
masses, they do not differ significantly
in their chemical behavior.
Section 3.3(A) – Counting Atoms
Average Atomic Masses of Elements
Average atomic mass is the weighted
average of the atomic masses of the
naturally occurring elements.
Example with marbles (100 total)
25 marbles x 2.00 g = 50 g
75 marbles x 3.00 g = 225 g
Adding the masses gives
50 g + 225 g = 275 g
Divide this by the total number of marbles and you get an
average marble mass of 2.75 g
Section 3.3(A) – Counting Atoms
Average Atomic Masses of Elements –(continued)
Average atomic mass
How are the masses on the periodic table determined?
(KEY)
Section 3.3(B) – Counting Atoms
Objectives
HW – Notes on section 3.3 pgs 80-85
Students will be able to :
•Define mole in terms of Avogadro’s number, and
define molar mass.
•Solve problems involving mass in grams, amount in
moles and number of atoms of an element.
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms - the Mole
A mole (abbreviated mol)is the amount of
a substance that contains as many
particles as there are atoms in exactly
12 g of carbon-12.
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms – Avogadro’s number
The number of particles in a mole has
been experimentally determined in a
number of ways.
Avogadro’s number 6.011 1367 x 1023 – is
the number of particles in exactly one
mole of a pure substance.
For ours (and most purposes) Avogadro’s
number is rounded to 6.022 x 1023
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms – Molar Mass
The alternative definition of mole is
the amount of substance that contains
avogadro’s number of particles.
The mass of one mole of a pure
substance is called the molar mass of
that substance. Usually written in
units of g/mol.
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms – Gram/Mole Conversions
Amount of
element in moles
There are 3 mole equalities. They are:
1 mol = 6.02 x 1023 particles
1 mol = g-formula-mass
(periodic table)
1 mol = 22.4 L for a gas at
STP*
* STP = 0° C & 1 atm Pressure
Mass of element
in grams
Number of atoms
of element
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms – Conversions
There are 3 mole equalities. They are:
1 mol = 6.02 x 1023 particles
1 mol = g-formula-mass (periodic table)
1 mol = 22.4 L for a gas at STP*
These become. . .
1 mol
[-------------] [-------------]
6.02 x 1023 particles
or
6.02 x 1023 particles
1 mol
[-------------] [-------------]
[----]
[----]
1 mol
g-formula-mass (periodic table)
g-formula-mass (periodic table)
1 mol
22.4 L
or
OR
1 mol
22.4 L
1 mol
Reference Sheet
There are 3 mole equalities. They are:
1 mol = 6.02 x 1023 particles
1 mol = g-formula-mass (periodic table)
1 mol = 22.4 L for a gas at STP*
These become. . .
1 mol
[-------------] [-------------]
6.02 x 1023 particles
or
6.02 x 1023 particles
1 mol
[-------------] [-------------]
[----]
[----]
1 mol
g-formula-mass (periodic table)
g-formula-mass (periodic table)
1 mol
22.4 L
or
OR
1 mol
22.4 L
1 mol
Section 3.3(A) – Counting Atoms
Relating Mass to Numbers of Atoms – What does it mean?
g-formula-mass (periodic table)
For a
single
element it
is simply
the atomic
mass
found on
the
periodic
chart
Section 3.3(A) – Counting Atoms
Relating Mass to Numbers of Atoms – Examples
g-formula-mass (periodic table)
N
Ca
Ag
Ba
Section 3.3(A) – Counting Atoms
Relating Mass to Numbers of Atoms – What does it mean?
g-formula-mass (periodic table)
For a
COMPOUND
you will
need to
calculate
using
atomic
mass
found on
the
periodic
chart
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms – EXAMPLE
g-formula-mass (periodic table)
COMPOUNDS
Table Salt
NaCl
Water
H2O
Sugar
(glucose)
C6H12O6
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms – EXAMPLE
g-formula-mass (periodic table)
COMPOUNDS
inorganic salt
(soil fertilizer)
(NH4)2SO4
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms – MOLE PRACTICES
Practice 1
Practice 2
Practice 2 (Key)
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms – FUN WITH MOLES
Given :
2.860 m  ceiling height
9.630 m  room depth
10.620 m  room width
Atmosphere composition:
1 000 L = 1 m3
Nitrogen - 78.084%
Oxygen - 20.95%
How many mols of O2 and N2 are present in this
room?
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms – FUN WITH MOLES
Atmosphere
composition:
Nitrogen - 78.084%
Oxygen - 20.95%
Average lung volumes in healthy adults[7]
Volume
Inspiratory
reserve volume
Tidal volume
Expiratory
reserve volume
Residual
volume
Value (litres)
In men
In women
3.3
1.9
0.5
0.5
1.0
0.7
1.2
1.1
How many particles of O2 and N2 are taken in with
each breath?
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms – suggestions
1. Relax
2. Look for things you recognize
3. Estimate size of final answer
(with this comes do I remember using any of these before)
4. Set up and work out
5. Double check with estimate and
your sig figs
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms – MORE MOLE PRACTICES
Practice 3
TAKE-HOME
QUIZ
Practice 4
Practice 3 (KEY)
TAKE-HOME
QUIZ (KEY)
Practice 4 (KEY)
Section 3.3(B) – Counting Atoms
Relating Mass to Numbers of Atoms – Q - #4
100 atoms Ar
1x
Want to get to Mols...
102 atoms
Ar
1 mol
1 x 102 atoms Ar
------------------------- X ------------------------6.02 x 1023 particles
1
0.166 x 10-21 particles , which is equal to 1.66 x 10-1 x 10-21
Or more properly written as 1.66 x 10-22 mols Ar