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Atoms: The Building
Blocks of Matter
Unit 2

Introduction to the Atom
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Modern Atomic Theory
Subatomic Particles
Isotopes
Ions
Essential Standards and objectives:
1.1.1 Analyze the structure of atoms, isotopes, and ions.
1.1.2 Analyze an atom in terms of the location of electrons.
1.1.3Explain the emission of electromagnetic radiation in spectral form in terms
of the Bohr model.
1.1.4 Explain the process of radioactive decay using nuclear equations and half-life.
2.2.5 Analyze quantitatively the composition of a substance. (Introduction to moles)
The Atom: Smallest particle of an
element that retains the chemical
properties of the element.
Essential Questions:
What is an atom?
What is its structure?
What determines properties of an
element?
Atoms act in orderly,
predictable ways.
PHET Build an Atom




Use this in the search window
Share a computer with a partner
Individual work (write your answers on a
separate paper)
http://phet.colorado.edu/en/simulation/buildan-atom
Explain:
How does this
graphic demonstrate
the
characteristics of an
atom?
Make sure that you
include each graphic
(portions) in your
explanation
Reading: Cornell notes
Essential questions: What are the characteristics
of an atom?
In your notes: address both individual atoms
and atoms of an element
Modern Atomic Theory
2.
All matter:
Atoms of a given element:
3.
Atoms cannot be created nor destroyed in:
4.
In chemical reactions, atoms are
1.
Atomic Theory (cont.)
5.
To form compounds:
Law of Definite Proportions
Law of Multiple Proportions
Summary Table:
Atomic Structure- Subatomic Particles
Subatomic Location Charge Mass Importance
Particle
AMU
Designation of Atomic Structure

Atomic number (Z):


On the Periodic Table:
Mass number (A):

On the Periodic Table:
Representing atoms

Information from symbols and the Periodic
Table
What does this symbol tell us?
Protons:
Neutrons:
Electrons:
Designations for the Atomic
Structure
Atomic number (Z):
-
On the Symbol
On the Periodic Table
Mass number (A):
-
20
Ca
40.08
-
On the Symbol
On the Periodic Table
Review: What is Z? What is A?
Determine the number of protons, neutrons, and electrons.
31
32
Ga
Ge
Gallium
Germanium
69.72
72.61
Periodic Table: an Important Tool in Chemistry
but no set rules for what is included and where
16
S
S
32.06
16
32.06
How can we tell which is the atomic number
and the mass number?
AMU = relative measurement and used for comparison
Atomic
Mass Unit
AMU
The “amu” is defined as one twelfth of the mass of an atom of carbon-12 (with
6 protons and 6 neutrons) and has a value of 1.660538921×10−27 kg.
Organization of the Periodic Table
Columns – Groups
 All the elements have similar chemical and physical
properties
 All will chemically react in a similar way
 Names of groups
 Rows – Periods
 Elements have same number of energy levels

Isotopes
Isotopes
Isotopes:

Atoms of an element with different masses



Naturally occurring
Some are stable and some are radioactive
(unstable)
Isotopes of an element have the same number
of ___________ and
a different number of ______________.
Identifying Isotopes

Isotope Notation
1.
2.
On the Periodic Table, the number with the
Decimal point is:
Atoms of the Same Element
Atoms of the Same Element
Atoms of the Same Element
Atomic Mass


Weighted Average Mass of isotopes
Based on the percentage of each isotope
present.
Grades are often computed using a weighted
average.
Suppose that homework counts 10%, quizzes 20%,
Labs 10% and tests 60%.
 If:
homework grade is 92
quiz grade is 68
lab grade is 88
test grade is 81
What’s the overall grade?

Practice

Atomic Structure



Identify the number of proton, neutron, &
electrons of an atom of a specific element
Rounding the atomic mass on the Periodic Table
gives the mass of the most common isotope
Atomic Number & Isotopes



Correct symbol: A & Z
Complete the table
Complete the questions.
Practice:

Find the Average Atomic Mass


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Nucleus of each atom is represented
Graphic below #4 - explains #5-7
Isotopes: Atomic Number & Mass Number


Determine based on the chart – not the PT
2 Isotope notations
A
 Element – A (X-A)
Z
X
Find Average Atomic Mass
Atomic Number & Isotope
Isotopes: Atomic Number & Mass Number
Element
Isotope
Symbol
Atomic
Number
Z
Mass
Number
A
# of
protons
# of
neutrons
# of
electrons
What is the atomic mass of Nitrogen given:


N-14 is 99.64% of all nitrogen
N-15 is 0.36% of all nitrogen
What is the atomic mass of Indium if:


In-113 is 4.24%
In-115 is 95.72%
Calculate % Abundances from Masses

Requires the use of 2 equations and 2
unknowns.

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Isotope 1(X) + Isotope 2(Y) = Atomic Mass
X+Y=1
Substitute and solve for X or Y!
What are the percent abundances of
Vanadium if

V-50 + V-51 = 50.94 amu
What are the percent abundances for
Gallium if:

Ga-69 + Ga-71 = 69.72
Atom: Scanning Tunneling
Microscope
Study of atomic particles
Scanning Tunneling Microscrope
Development of the Atomic Theory

Essential Question: Why do elements have
different properties?
.
...............
Development of the Modern Atomic Model
Ancient Question
Atomic investigation
Bohr
Quantum Model

Electron Cloud model of
the atom
Representing atoms with the Bohr model
Representing atoms with the Bohr Model
Bohr Model – Simplified but Useful Model
Group
1
P1
P2
P3
Group Groups
2
2-12
Group
13
Group
14
Group
15
Group
16
Group
17
Group
18
Bohr Model & the Periodic Table
Making Conclusions
Compare and Contrast


Why are elements placed in a group (column)?
Why are elements placed in a period (row?)
Changing an Atom
Changing An Atom
Ions



Atoms can lose or gain electrons when bonding to
make ionic compounds
We keep track of the number of electrons that can be
lost or gained with oxidation numbers (also known
as charges)
Ions are charged particles –when an atom has too
many or too few electrons to be neutral
 No change to the nucleus
 Proton and neutrons stay the same number.
Ions – Charged Particles
7. When atoms of elements form ions
(__________ __________, they must either
__________ or _______ valence electrons.
Gain/lose? Charge
Metals
Non-metals
Ion type?
Why are ions important?

The ___________________ charged particles
are like a magnet.

Therefore, they are strongly held together in
an ______________ _____________
forming an _____ ________________.
Representing atoms with the Bohr Model
Ions
Lithium atom - Lithium ion
p+
p+
nº
nº
eeFluorine atom Fluorine ion
p+
p+
nº
nº
ee-
Ion Symbol
Ions and Charge
Net electric charge
Note
change
8
Ions and Charges for Representative Elements
(Oxidation number keep track of electrons)
Ion Making
Making an ion of an
alkali metal,
First column in the
periodic chart,
Leaves all the ions
with a plus one
charge
And they’re all a
whole lot smaller
than they were
before.
Second column over,
Alkaline earths,
Loses 2 electrons easily,
So their ions all have
a plus 2 charge,
And they’re smaller
than their neighbors
to the left.
Next door, aluminum,
the 3rd step over
has 3 electrons
It’d like to have removed.
When they are gone, it
has a +3 charge,
And, by gosh!, It’s even
smaller than the
“lefter” two.
But add one electron
To the halogen group,
So they all have a
Negative one charge.
They get 8x bigger than
They were before.
Puffed up, very large.
Sulfur and oxygen
need 2 electrons to
give each a full and
complete electron shell.
Thus, minus 2 is their
ionic charge.
And they’re a little larger
Than the “Hal-ions”.
Add three electrons to the nitrogen group.
So that group has a triple minus charge.
And the pattern we see makes it very clear.
Negative ions are large!
Mole
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Resources for students
http://molechemistry.info/
Nuclear Chemistry
Neutron to
Proton Ratio
Types of Radiation
Alpha Decay
Beta decay
Gamma Decay
Radiation Strength
Nuclear Equations
1.
2.
3.
4.
5.
6.
1 H + 9 Be ---> 6 Li + ?
1
4
3
27 Al + 4 He ---> 30 P + ?
13
2
15
24 Mg  24 Mg + ?
12
12
238 U  234 Th + ?
92
90
14 C  0 e + ?
6
-1
239 Pu + 4 He  242 Cm +
94
2
96
?
Nuclear Equations Practice Website
Half-life


Measure of Radioactive decay rate.
Measured as the time it takes for ½ of a
sample of radioisotope’s nuclei to decay into
its products.
Half Life
Decay of a radioisotope
Number of
Elapsed time
Half-Lives
0
0
Amount
remaining
100 g
1
1.5 year
50 g
2
3 years
25 g
3
4.5 years
12.5 g
Half Life Problems

How much of a 100g sample of an unstable
isotope remains after 25 years if the half life is
5 years?
3.1 g
Half Life Problems

How much of a 60g sample of an unstable
isotope remains after 2 days if the half life is
12 hours?
7.5 g
Half Life Problems

How much of a 20 g sample of an unstable
isotope remains after 6 sec if the half life is
0.5?
0.005 g
Atomic Nucleus
(also known as nuclide)

Mass

Energy

Volume
Radioactive Isotopes
A radioactive isotope has an unstable nucleus
that undergoes spontaneous changes.
- Emits particles and energy
-
Transmutates into another element
Particles emitted from a
radioactive isotope
Type
Symbol
Charge
Mass
Nuclear reactions
Total number of atomic numbers and the total
mass numbers must be equal on both sides of
the equation.
Examples:
Radioactive decay
No 2 radioactive isotopes decay at the same rate.
Therefore, decay rate can be used to identify
the isotope. Decay is measured by half life.
Fission and Fusion
Origins of Element
Got Calcium
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Where are most elements created?
When was H and He created?
What elements are made by small stars?
What additional elements are made by large
stars?
What elements are made by supernovae (large
exploding stars)?
Teachers' Domain: The Origin of the
Elements
Teachers' Domain: The Elements:
Forged in Stars