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Transcript
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Bohr Models and Isotopes
Agenda:
1.
Calculating protons,
neutrons, and
electrons warm up
2.
Calculation practice
3.
Bohr models
4.
Atomic brother
01/22
Please pick up
the handout
on the front
table and
begin filling
in the front
side key and
atom 
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Atomic Structure Practice
Bohr Models
Valence Electrons
Identifying Elements
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Let’s Review…

What was Bohr’s contribution to our understanding of atomic
structure?

What does a Bohr model look like?

How do we determine the number of protons in an atom of an
element?

How do we determine the number of electrons in an atom of
an element?

How do we determine the number of neutrons in an atom of
an element?
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Let’s Review…
What was Bohr’s contribution to our understanding
of atomic structure?
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Let’s Review…
What was Bohr’s contribution to our understanding
of atomic structure?

Orbiting electrons

Energy levels
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Let’s Review…
What does a Bohr model look like?
+
Let’s Review…
What does a Bohr model look like?
+
+
Let’s Review…
What does a Bohr model look like?
+
Let’s Review…
How do we determine the number of protons in an
atom of an element?
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Let’s Review…
How do we determine the number of protons in an
atom of an element?
Protons = 3
3
Li
Lithium
7
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Let’s Review…
How do we determine the number of electrons in an
atom of an element?
+
Let’s Review…
How do we determine the number of electrons in an
atom of an element?
Protons = 3
3
Li
Lithium
7
Electrons =3
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Let’s Review…
How do we determine the number of neutrons in an
atom of an element?
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Let’s Review…
How do we determine the number of neutrons in an
atom of an element?
Protons = 3
Atomic mass – Atomic Number
7 – 3 = 4 neutrons
3
Li
Lithium
7
Atomic
mass = 7
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Bohr Model Practice
Create models of atoms of the elements assigned by your teacher
using your periodic table for reference.
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Valence Electrons
Valence electrons determine the chemical
properties of an element.
 Reactivity:
filling the outer energy level
Images: www.cyberlepsy.com and www.teachervision.com
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Isotopes, Ions and Valence
Electrons
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Isotope

Atoms of the same element with different
numbers of neutrons in the nucleus.

Causes a different atomic mass.

Example:
Taken from:
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Isotope
Question: What changes when you add or
take away a neutron from an atom?
Answer: The atomic mass changes: it increases
when a atom has an extra neutron, and
decreases when it has one less neutron.
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Isotope
Question: Which of the atoms below are
isotopes for Sodium-12?
Hint: Use your periodic table to make calculations and compare.
Choice:
Element
Protons
Neutrons
Electrons
A.
B.
C.
Na
Na
Na
11
12
11
12
12
13
12
11
11
Answer: Sodium’s atomic # is 11, so it has 11
protons and 11 electrons. Choice C has 13 neutrons
compared to Sodium-12, so it gained a neutron.
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Ion




Atoms that have lost or gained electrons.
Causes a different electric charge
(positive or negative)
Example:
Taken from:
http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/chemistry/chemistr.htm
Click here for animations describing this
further.
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Ion
Question: What changes when you add an
electron to an atom?
Answer: The electric charge changes to
become negatively charged.
(Since electrons are negatively charged,
adding an electron will cause the atom to
be negatively charged.)
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Ion
Question: What changes when you take
away an electron to an atom?
Answer: The electric charge changes to
become positively charged.
(Since electrons are negatively charged,
taking away an electron will cause the atom
to be positively charged.)
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Ion
Question: Which of the atoms below are ions?
Hint: Use your periodic table to make calculations and compare.
Choice:
Element
Protons
Neutrons
Electrons
A.
B.
C.
O
O
O
8
9
8
8
8
7
9
8
8
Answer: Oxygen’s atomic number is 8, so a neutral atom would have 8
protons and 8 electrons. Choice A has 9 electrons, making it an ion.
Bonus questions:
- Is this ion negatively or positively charged?
- Which answer choice shows an isotope?
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Valence Electrons
 Electrons
in the outermost energy level of an
atom that determine the element’s chemical
properties.

For Elements #1 – 30, there can be 8 valence
electrons in the outer shell
Taken from: http://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.html
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Valence Electrons
 If an element is stable, it has all 8 valence electrons.

Elements with less than 8 valence electrons are
reactive.

For example, Sodium, which
has 1 valence electron, reacts
with Chlorine, which has 7.

When the atoms combine, they
have a total of 8 valence
electrons (1 + 7 = 8)

NaCl is a stable molecule, but
Na and Cl on their own are
reactive.
Taken from:
http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%
lectures/chemistry/chemistr.htm
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Valence Electrons
 The periodic table is organized with similar
valence electrons in the same columns.
 Which
columns would
react?
 Which
are
stable?
 Can
you
predict which
will react with
each other?
Taken from: http://cactus.dixie.edu/smblack/chem1010/lecture_notes/3A.htm
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Valence Electrons
Question: Where are the valence electrons
located?
Answer: Valence electrons are located in the
outer shell.
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Valence Electrons
Question: How many valence electrons need to
be in the outer shell for it to be stable?
Answer: 8
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Valence Electrons
Question: Which of the atoms would react with
each other?
Hint: Use your periodic table for help. Notice the Roman
Numerals above each column tell you the number of valence
electrons: I = 1, II = 2, III = 3, IV = 4, V = 5, VI = 6, VII = 7, VIII = 8.
Hydrogen
Helium
Argon
Aluminum
Bromine
Calcium
Answer: Hydrogen and Bromine would react.
Hydrogen is in column 1, so it has 1 valence
electron. Bromine is in column 7, so it has 7
electrons. 1 + 7 = 8!
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Reactivity & Valence
Electrons
VIDEO:
The Reaction Between Water and the First Group Elements
Group 1: Alkali Metals
Lithium, Sodium, Potassium, Rubidium, Cesium, Francium
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Let’s look at their
atomic structure.
Sodium
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Let’s look at their
atomic structure.
Potassium
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Let’s look at their
atomic structure.
Cesium