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LIVE INTERACTIVE LEARNING @ YOUR DESKTOP
The Periodic Table and Bonding —
Introducing a Free Online Resource for Middle
School Chemistry
Presented by: James Kessler
January 17, 2013
6:30 p.m. – 8:00 p.m. Eastern time
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Introducing today’s presenter…
James Kessler
Manager, K-8 Science Education
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Middleschoolchemistry.com
Big Ideas about the Very Small
Chapter 4: The Periodic Table
and Bonding
Welcome
What is middleschoolchemistry.com?
Free online resource for teaching
basic concepts in chemistry at the
middle school level.
Six chapters of activity-based lesson
plans which align with state standards
in physical science and inquiry.
Two main goals:
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Help students understand common
every day observations on the
molecular level.
•
Help students to design and
conduct scientific experiments.
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What’s in a Chapter?
•
Lesson Plans (5E):
– Hands-on activities
– Student Activity Sheets
– Multimedia
– Extra Teacher Background
•
Student Reading
•
Test Bank
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Goals of the Webinar
•
Demonstrate selected activities and
animations from the lessons in Chapter 4
to show how they can be used with
students
•
Review some basic chemistry concepts
covered in the lessons
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Big Idea for Chapter 4:
What does the periodic table tell us about atoms and why do
atoms bond together to make molecules?
Use the “Fascination Number Line” to indicate your level of
fascination with this question.
0
Have never
thought about it
and happy that
way
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Willing to listen if
it doesn’t take too
long
10
Stay up nights
pondering this
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Lesson 4.1
Protons, Neutrons, and Electrons
Engage
Explore
Explain
Evaluate
Extend
Discussion: What are the three tiny particles that make up an atom?
Introduce a version of the model that students
will be working with throughout the chapter.
Protons – In the center or nucleus of the atom.
Positive electrical charge.
Neutrons – In the nucleus of the atom. No
charge.
Electrons – Outside the nucleus. Negative
electrical charge. Same number of electrons as
protons.
Positive protons and negative electrons attract
each other.
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Protons and Electrons
Engage
Explore
Explain
Evaluate
Extend
Protons have a positive charge.
Two protons repel each other.
Electrons have a negative charge.
Two electrons repel each other.
But a proton and an electron have
opposite charges.
A proton and an electron attract each
other.
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The Hydrogen Atom
Engage
Explore
Explain
Evaluate
Extend
In the hydrogen atom, and every other
atom, the negatively charged electron is
attracted to the positively charged proton.
This attraction is what holds the atom
together.
The cloud shows the region around the
nucleus where the electron is most likely
to be. It is not possible to know its exact
location at any time.
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Static Electricity is Protons and
Electrons Attracting
Engage
Explore
Explain
Evaluate
Extend
Pull a strip of plastic between
your fingers.
Bring the plastic near your
fingers to see what happens.
The plastic is attracted to your
fingers.
Why?
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Transferring Electrons
Engage
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Explore
Explain
Evaluate
Extend
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Questions So Far?
Type your questions or comments in the chat.
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Lesson 4.2: The Periodic Table
We will focus on the first 20
elements: from hydrogen
(H) to calcium (Ca).
Atomic number: The
number of protons in the
nucleus.
Atomic mass: Made up of
the mass of the protons,
neutrons, and electrons of
the atoms of that element.
The proton and neutron
have about the same mass
and the electron is about
1/2000 as massive.
Why the weird decimal
number for atomic mass?
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Periodic Table: Elements 1-20
Carbon has 6 protons in the
nucleus but it has an atomic mass
of 12.01.
This means that some carbon
atoms must have more than 6
neutrons.
The vast majority of carbon atoms
have 6 neutrons but some small
percentage have 7 neutrons.
That’s what causes the average
atomic mass to be just over 12.00.
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Play a Periodic Table Card Game
20 sheets – One for each of the first
20 elements.
Upper right hand corner is the
element card.
Cards on the left are about protons,
neutrons, and electrons.
Cards on the right are about energy
levels.
100 cards on the left are for the first
card game.
80 cards on the right are for the
second card game.
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Play a Periodic Table Card Game
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Interpreting the Periodic Table
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Lesson 4.3 - The Periodic Table and
Energy Level Models
An atom is spherical.
The atom’s electrons are in regions surrounding the nucleus
called energy levels.
The first energy level is closest to the nucleus and can hold a
maximum of 2 electrons.
The second energy level is further from the nucleus and can hold
a maximum of 8 electrons.
The third energy level is still further from the nucleus and can
hold a maximum of 18 electrons. After the third level has 8, the
next two electrons go into the fourth level, and then electrons
begin to fill the third level again until it has 18.
The fourth energy level can hold a maximum of 32 electrons.
What is this atom?
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Electrons in Energy Levels
Atoms in the first row
have 1 energy level.
Atoms in the second row
have 2 energy levels.
Atoms in the third row
have 3 energy levels and
so on.
The number of energy
levels is called the
principle quantum
number (n).
The number of electrons
on an energy level = 2n².
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Play a Periodic Table Card Game
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Chat Discussion and Questions
Have you done activities similar to the Periodic
Table card games?
What other ideas do you have?
Do you have any questions?
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Periodic Trend – Atomic Size
Atomic size decreases as atomic number increases from left to right across a
row.
Electrons are attracted and pulled toward the nucleus more as the number of
protons (positive charge) increases.
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Periodic Trend – Atomic Size
Graph shows that the relationship between atomic size and atomic number
has a periodic, or up and down, trend.
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Periodic Trends- Ionization Energy
Ionization energy is the energy required to remove an electron from the
outer energy level of an atom. The trend in ionization energies is also
periodic with the lowest ionization energy on the left and the highest on
the far right of any row.
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Elements in the Same Group React in a
Similar Way
Sodium in Water
Sodium and potassium have
a similar reaction with water
but the reaction of calcium
and water is different.
Potassium in Water
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Calcium in Water
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Elements in the Same Group React in a
Similar Way
Sodium in Acid
Sodium and potassium
have a similar reaction
with acid but the
reaction of calcium and
acid is different.
Potassium in Acid
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Calcium in Acid
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Chat Discussion and Questions
What will be most challenging for your students
in learning the Periodic Table?
Do you have any questions?
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Lesson 4.4 - Energy Levels, Electrons,
and Covalent Bonding
Two hydrogen atoms. Each has one proton and one
electron.
If they get close enough, the electron from each hydrogen
atom feels the attraction from the proton of the other
hydrogen atom.
If the attraction is strong enough in both directions, and
there is room for the electrons on the outer energy levels
of both atoms, the atoms share electrons in a covalent
bond.
Sharing electrons means that the electrons now occupy a
region where they are attracted by the nucleus of both
atoms instead of just the one they started with.
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Covalent Bond - Hydrogen Molecule
The atoms are drawn together by the
mutual attraction of the protons and
electrons in the two atoms.
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Covalent Bond - Water Molecule
The electron in hydrogen is attracted to the
protons in oxygen. And the electrons in oxygen
are attracted to the proton in hydrogen.
If the attraction is strong enough in both
directions and there is room for the electrons in
the outer energy level of both atoms, the atoms
share electrons in a covalent bond.
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Covalent Bond – Water Molecule
The atoms are drawn together by
the mutual attraction of the protons
and electrons in the two atoms.
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Water’s Covalent Bond is Polar
The covalent bond in water is polar.
Although electrons are shared between oxygen
and hydrogen, the oxygen has a stronger attraction
for electrons so the electrons are not shared
exactly equally.
The electrons spend more time near the oxygen
part of the molecule, making that part slightly
negative.
Since the electrons spend more time near the
oxygen, the hydrogen part of the molecule is
slightly positive.
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Hydrogen and Oxygen in Water
An electric current in water can cause
electrons to be transferred between
water molecules and the electrodes.
This causes the oxygen and hydrogen
in the water molecules to come apart
and to be released as hydrogen and
oxygen gas.
Twice as much hydrogen is produced
than oxygen because for each water
molecule there are two hydrogen
atoms and one oxygen atom.
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Atoms Can Form Double Covalent Bonds
The electrons in each oxygen atom are attracted to the
protons in the other oxygen atom.
If the attraction is strong enough in both directions and
there is room for the electrons in the outer energy level
of both atoms, the atoms share electrons in a covalent
bond.
Since both atoms are the same, they have the same
attraction for electrons and the sharing is equal.
This is different from the water molecule
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Oxygen Atoms Form Double Covalent Bonds
The atoms are drawn together by the
mutual attraction of the protons and
electrons in the two atoms.
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Lesson 4.5 – Energy Levels, Electrons,
and Ionic Bonding
Salt is sodium chloride which is made
up of positive sodium ions and
negative chloride ions.
The ions attract each other according
to their opposite charges and form a
cubic crystal structure.
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Ionic Bonding in Sodium Chloride
The chlorine has a stronger pull on the electron from
sodium than the sodium has for an electron from
chlorine.
An electron is transferred from the sodium to the
chlorine.
Now the sodium has 11 protons but only 10 electrons.
The extra proton makes it a positive ion.
The chlorine has 17 protons but now has 18 electrons.
The extra electron makes it a negative ion.
The oppositely charged ions attract each other forming
an ionic bond.
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Ionic Bonding
Electron transfer causes sodium
and chlorine atoms to become
positive and negative ions which
attract.
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How Can a Clay Object Float?
Soft silver metal, sodium, is placed in a
container filled with chlorine gas.
A drop of water is added to the sodium
which reacts and removes the sodium’s
protective tarnish coating.
The exposed sodium metal reacts with the
chlorine gas.
An extremely reactive metal and a
poisonous gas combine to make an ionic
compound (sodium chloride) that we eat.
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Students Model the Ionic Bonding
in a Sodium Chloride Crystal
Students use Styrofoam balls and tooth
picks to make repeating alternating
patterns of ions.
The teacher then stacks each layer to form
a model of a 3-D crystal of sodium
chloride.
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Ions that Lose or Gain More than
One Electron
Chlorine has a stronger attraction for the
electrons in calcium than calcium has for the
electrons in chlorine.
Two electrons are transferred from the
calcium atom – One each to the two chlorine
atoms.
This gives each chlorine an extra electron so
each becomes a negative Cl- ion .
The calcium atom now has two more protons
than electrons so it becomes a positive Ca2+
ion.
The positive and negative ions attract each
other to form calcium chloride (CaCl2)
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Ionic Bond in Calcium Chloride
Electron transfer causes calcium
and chlorine atoms to become
positive and negative ions which
attract.
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Ready to Try it?
What content would be useful to you in your classroom?
Any final questions?
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Thanks to today’s presenter…
James Kessler
Manager, K-8 Science Education
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Thank you to the sponsor of today’s
web seminar:
This web seminar contains information about programs, products, and services
offered by third parties, as well as links to third-party websites. The presence of
a listing or such information does not constitute an endorsement by NSTA of a
particular company or organization, or its programs, products, or services.
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Gerry Wheeler, Interim Executive Director
Zipporah Miller, Associate Executive Director,
Conferences and Programs
Al Byers , Ph.D., Assistant Executive Director,
e-Learning and Government Partnerships
Flavio Mendez, Senior Director, NSTA Learning
Center
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Brynn Slate, Manager
Jeff Layman, Technical Coordinator
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