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Patterns and the
Periodic Table
Featuring the Return of Bohr-Rutherford Diagrams
and the Periodic Table
SNC2D
The Periodic Table
• Designed by Mendeleev in 1869
• Organizes matter based on its properties
and atomic number
• Allowed for the prediction of then
unknown elements
Periods and Families
• The rows in the periodic table are known as periods.
• The columns in the periodic table are known as groups.
• Groups tend to have similar properties.
• Major groups (multiple columns):
– Metals
– Non metals
– Metalloids
• Single column groups:
–
–
–
–
Alkali metals
Alkali earth metals
Halogens
Noble gases
Properties Compared
• Metals
–
–
–
–
–
Nickel (Ni)
Solid
Shiny
Malleable
Conductor
• Non-Metals
–
–
–
–
–
Sulphur (S)
Solid, liquid, or gas
Dull
Brittle
Insulator
Atomic Theory of Matter
• Dalton brings back Democritus’ idea of
the atom as an indivisible particle.
• Dalton gives us the “billiard ball” model.
Subatomic Particles
• Atomic theory is revised as subatomic
particles are discovered.
– Electrons and Protons
• “Raisin Bun” model
• Saturn/solar system model
– Neutrons
• Bohr – Rutherford model
Modern View of the Atom
• Protons, neutrons, electrons
• Mass measured in atomic mass units (amu)
which is equal to 1.66 x 10-24g
Subatomic
Charge
Particle
Symbol
Mass
(amu)
Electron
1-
e-
1/2000
Proton
1+
p+
1
Neutron
0
n0
1
The Bohr-Rutherford Model
-used to show the arrangement Helium Atom
of electrons in the atom
• 2 positive protons in
nucleus
• 2 neutral neutrons in
nucleus
• 2 negatively charged
electrons in the first
energy level
– 2-8-8-2 are the
number of electrons
in each energy level
for the first 20
elements
How to Draw a
Bohr Diagram
• Find your element on the periodic
table.
Si
Element 14 has
the symbol Si
and 14 electrons
• Determine number of electrons,
which for a neutral atom is equal to
the number of _________, which
is equal to the ________________
Si
• Place the element symbol in the
middle.
• Draw in the energy levels –
(determine which period (row)
your element is in)
• Add electrons following the 2-8-8-2 Check your work: Count your
pattern for the first 20 elements
electrons per shell and your
total electrons!
Standard Atomic Notation
(for a neutral atom)
Atomic symbol
Mass number
28
14
Atomic number
Si
Number of
protons
Atomic
number (14)
14 p+
Number of
electrons (for
neutral atom)
Atomic
number (14)
14 e-
Number of
neutrons
Mass number
– Atomic
number
(28-14=14)
14 n0
How to Draw a
Bohr-Rutherford Diagram
• Determine the number
of protons, neutrons,
and electrons
Element 14 has 14
electrons, 14 protons,
and 14 neutrons
• Place the number of
protons and neutrons
for the element in the
middle
• Draw in the energy
levels
• Add electrons following
the 2-8-8-2 pattern for
the first 20 elements
14 p+
14 n0
Homework
1.
2.
Refer to the periodic table to name and write the symbols for the following
elements: [K]
a.
b.
c.
d.
e.
f.
A halogen of the second period
The alkaline earth metal in the fifth period
The noble gas with the smallest atomic number
The non-metal in the fifth period with seven outermost electrons
The alkali metal of the fourth period
The metal of the third period with three outermost electrons
g.
The unreactive gas of the second period.
Try drawing Bohr-Rutherford diagrams for each of the following elements: [C]
[I]
a)
O
b) Al
c) Ne
d) K
3. Imagine that a chemist discovers a new element with atomic number 119. [I]
a)
b)
c)
Use the periodic table to predict what chemical family this element would belong to.
How many outer electrons would an atom of this element have?
Predict one physical property and one chemical property of this element.
4. Why are atoms electrically neutral? [K]
Lewis Dot Diagrams
The electrons in the outermost shell
are called ?
Lewis Dot Diagrams
The electrons in the outermost shell
are called valence electrons .
Lewis Dot Diagrams
The electrons in the outermost shell
are called valence electrons .
Lewis Dot Diagrams are abbreviated
Bohr Diagrams that show just these
outermost electrons, e.g.:
Valence Electrons and
Families
Note that both hydrogen (H) and
potassium (K) have just ? electron in
their outermost shell.
Note also that these elements are both
found in the ? column of the periodic
table.
This is not a coincidence!
Valence Electrons and
Families
Note that both hydrogen (H) and
potassium (K) have just 1 electron in
their outermost shell.
Note also that these elements are both
found in the ? column of the periodic
table.
This is not a coincidence!
Valence Electrons and
Families
Note that both hydrogen (H) and
potassium (K) have just 1 electron in
their outermost shell.
Note also that these elements are both
found in the 1st column of the periodic
table.
This is not a coincidence!
Valence Electrons and Groups
All elements in the same group
(column) have the same number of
electrons in their outermost shell
(ref. p. 150)
It is these electrons that determine the
behavior of the element (chemical
properties), including how it reacts
with other elements – and how it forms
ions.
Homework
1.
For each of the elements that you drew a Bohr-Rutherford diagram in
question 2, draw its Lewis Structure. [C] [I]
a) O
b) Al
c) Ne
d) K
1.
Which of the above elements would you expect to be the most reactive
and why? [K]
1.
Which of the above elements would you expect to be the least reactive
and why? [K]
Credits
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http://commons.wikimedia.org/wiki/File:IUPAC_Periodic_Table.PNG
http://commons.wikimedia.org/wiki/File:Atomic_size_periodic_table.svg
http://commons.wikimedia.org/wiki/File:Periodic_table_fluorine.svg
http://commons.wikimedia.org/wiki/File:Nickel_kugeln.jpg
http://commons.wikimedia.org/wiki/File:Sulphur2.jpg
http://commons.wikimedia.org/wiki/File:Radiosity.png?uselang=en-gb
http://commons.wikimedia.org/wiki/File:Bohr_model.jpg
http://commons.wikimedia.org/wiki/File:Helium-Bohr.svg