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The Structure of Matter
(Science 10 Review)
The Atom
Do Now
 Place your lab safety contract into the blue
bin (by station 8).
 Pick-up both a work booklet and a periodic
table (by station 5)
Plan for the Week
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Science 10 Review
 What is an element? Atom? Neutron? Proton? Electron?
 Bohr and Lewis Dot Diagrams
Look at why we often need to dissolve things in water to do
chemical reactions
Differences between electrolytes and non electrolytes
The Plan
Explain how science & technology have
influenced, & been influenced by historical
development & societal needs.
1. Science 10 chemistry review
2. Learn about atoms & how to diagram them
 Bohr diagram
 Lewis dot diagram
3. Practice drawing a diagram of an atom
Lab Safety Rap
Elements
 A pure substance cannot be broken down
into simpler substances by chemical means.
 You find these on the periodic table.
 The smallest part of an element is an atom.
Atom
 The basic unit of matter.
 It is made up of
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Protons – positively charged particles located in
the nucleus of an atom (p+).
Neutrons – a neutral particle located in the
nucleus of an atom (no).
Electrons – a negatively charged particle located
in the region surrounding the nucleus of an atom
(e-).
Atoms
Protons
Neutrons
Electrons
Atoms
Particle
Location
Charge
Proton
Nucleus
1+
Neutron
Nucleus
0
Electron
Surrounding
Nucleus
1–
Joke for the Day
 A neutron walks into a bar, sits down
and asks for a drink. Finishing, the
neutron asks "How much?"
 The bartender says, "For you, no
charge."
Atoms
 Atomic Number – this is the number of
protons within the atoms.
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Hydrogen has an atomic number of 1 which
means that it has 1 proton.
Sulfur has an atomic number of 16 which means
that it has 16 protons.
Carbon = _______ p+
Sodium = _______ p+
 It is the number of protons which makes one
element different from another.
Atoms
 Atomic Mass - the average mass of the
atoms of an element including all isotopes.
 To calculate the number of neutrons, take the
atomic mass and subtract the protons.
 Neutrons = atomic mass – protons
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Nitrogen = 14 – 7 protons = 7 neutrons
Fluorine = 19 – 9 protons = 10 neutrons
Helium = 4 Oxygen =16 -
Atoms
 Mass Number – the total number of protons
and neutrons in an atom.
 Mass = neutrons + protons
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Oxygen = 8 protons + 8 neutrons = 16
Oxygen = 8 protons + 9 neutrons = 17
These different masses are the isotopes of
oxygen.
Practice
 Try #2 & 3 (p. 8) on your own.
 When done-Read the bottom of page 7 from
Science 20 on electrical characteristics.
Sketching Diagrams of Atoms
 Niel Bohr developed the idea that only a
certain number of electrons are able to
occupy an energy level.
 An energy level is a specific region
surrounding the nucleus that is available for
electrons.
 Level 1
 Level 2
Sketching Diagrams of Atoms
Step 1: Use the atomic number and atomic
mass listed on the periodic table to determine
the number of protons, electrons, and
neutrons (PEN) that make up the atom.
Step 2: Draw the nucleus of the atom with the
appropriate number of protons and neutrons
within the nucleus.
Step 3: Use dots to represent the electrons in
each energy level that surrounds the nucleus.
Sketching Diagrams of Atoms
 Each energy level holds a specific # of e-.
The number of electrons in a given energy
level is shown by the number of elements
in each period (row) on the periodic table.
Sketching Diagrams of Atoms
 E.g.,. The first energy level can hold two electrons. This
is shown by the first period having only two elements (H
and He). The second energy level can hold eight
electrons. This is shown by the second period of the
periodic table having eight elements: Li, Be, B, C, N, O, F,
and Ne.
Bohr Diagram of Chlorine Atom
Step 1: Determine the number of protons, electrons, and
neutrons.
P: number of protons = atomic number
= 17
E: number of electrons = number of protons (b/c it is an
atom)
= 17
N: number of neutrons = atomic mass – number of protons
= 35.45 – 17
= 18 rounded
Bohr Diagram of Chlorine Atom
Step 2: Draw the nucleus of the atom. The
nucleus of the atom contains the protons
and neutrons.
17p
18n
Bohr Diagram of Chlorine Atom
Step 3: Draw the electrons in their appropriate
energy levels.
Chlorine has 17 electrons. The first energy level
can hold 2 electrons, leaving 15 more to
place.
The second energy level can hold 8 electrons,
leaving 7 more to place.
The third energy level can hold 8 electrons, but
there are only 7 remaining. The final 7 will fit
on the third energy level.
Bohr Diagram of Chlorine Atom
Bohr Diagram of Chlorine Atom
Here is a more concise way to represent the
final Bohr diagram
7e8e2e17p
18n
Practice
 Try #5 a, d, & g (p. 9 of textbook)
Lewis Dot Diagrams
 Is a representation of an atom that
shows only the valence electrons.
 Valence electrons are the electrons in
the outermost (last) energy level.
Lewis Dot Diagrams
Lewis Dot Diagrams
Step 1: Write the chemical symbol. This symbol will
represent the inner electrons and the nucleus.
Step 2: Determine the number of electrons in the
outermost energy level. (The column number will help
you to do this).
Step 3: Use a dot to represent each electron in the
outer energy level. The dots are placed on the north,
east, south, or west sides of the symbol. Each
position only has room for two electrons. Double up
on electrons only after all the other positions contain
at least one electron.
Lewis Dot Diagrams
Atom
Oxygen
Bohr Diagram
Lewis Dot Diagram
Lewis Dot Diagrams
Atom
Oxygen
Bohr Diagram
Lewis Dot Diagram
8p
8n
O
Lewis Dot Diagram for Oxygen
Lewis Dot Diagrams
Atom
Bohr Diagram
Lewis Dot Diagram
P
Phosphorus
15p
16n
Lewis Dot Diagram
Practice
 Try #6c & d (p. 10) on your own.
Octet Rule
• All atoms strive to complete the outer shell with
electrons and thus become a stable atom. They can
complete these outer shells by gaining, losing or
sharing electrons from other atoms.
Gaining Electrons
• Chlorine has 7 electrons in the outer shell & will
gain ___ electron to complete the shell.
• Since it has gained ___ electron, it now has a 1-
charge and is now a charged atom called an ion.
• Ion – an electrically charged atom or group of
atoms. A negatively charged ion is called an
anion.
Losing Electrons
• Sodium has 1 electron in its outer shell and will
lose this electron to complete the outer shell.
• Since it has lost an electron, it now has 1+ charge
and is now a charged atom called an ion.
• A positively charged ion is called a cation.
If an atom gains electrons, it becomes negatively
charged. If it loses electrons it becomes
positively charged.
The Periodic Table
Metals vs. Non-Metals
 Metals tend to form
positively-charged
ions (cations)
 Non-metals tend to
form negativelycharged ions (anions)
Assignment
 Pg. 5 & 6 of workbook.
Assignment
 Page 8 practice # 1
 Page 9 practice #5
 Page 10 practice #6
Answers
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Page 8 practice # 1 - 3
#1
a) Protons are found in the nucleus and have a
positive charge. The # of protons is the same as the
atomic number.
b) Neutrons are found inside the nucleus and have no
charge. They add mass to the atom.
c) Electrons are found surrounding the nucleus and
have a negative charge. They play a role in
bonding.
 # 2 & 3 are in the back of the textbook
Answers
a) Carbon
b) Hydrogen
c) Aluminium
Pg. 9 # 5
Answers
d) lithium
e) sodium
f) fluorine
Pg. 9 # 5
Answers
Pg. 9 # 5
g) neon
h) helium
Pg. 10 #6 is in the back of the textbook