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WARM UP RIDDLE
You are shown five cards face down on a table.
You are told that the five cards are as follows: 1
Joker and 4 Aces (each of a different suit).
 Given the following information, determine the
position for each card.

WARM UP RIDDLE
The club is to the immediate right of the heart.
 Neither the diamond nor the joker is next to the
spade.
 Neither the joker nor the diamond is next to the
club.
 Neither the diamond nor the spade is next to
the heart.

WARM UP RIDDLE
THE PERIODIC TABLE
THE NEED FOR BETTER CLASSIFICATION
By the 1850s, chemists had successfully
identified 58 elements and they were not sure how
many more remained to be discovered.
 Using chemical symbols (like H for Hydrogen),
chemists were able to communicate about the
elements and they were often grouped together in
families.
 Unfortunately, the elements within these families
often behaved very differently from each other and
it became clear that a better system was needed.

DMITRI MENDELEEV


Born in 1834 in a village
outside of Tobolsk,
Siberia.
He was instrumental in
developing the modern
Periodic Table.
DMITRI MENDELEEV


Mendeleev felt as though
elements could be
grouped according to their
atomic masses and other
similar properties.
By arranging the elements
in order of increasing
atomic mass, Mendeleev
found that the properties
of the elements repeated
at periodic intervals.
DMITRI MENDELEEV
DMITRI MENDELEEV



Throughout his research
he encountered places
where the periodic
patterns were broken. He
decided to leave these
spaces blank.
Mendeleev was even able
to use his table to predict
the existence of then
unknown elements.
His predictions were
amazingly accurate.
Germanium
(Ge)
Property
Predicted
Actual
Atomic Mass 72
72.6
Density
(g/cm3)
5.5
5.35
Colour
Dirty gray
Grayishwhite
Action on
strong
heating
XO2
GeO2
Effect of
water
none
none
Effect of
Alkalis
slight
none
Effect of
Acids
slight
none
THE MODERN PERIODIC TABLE
THE MODERN PERIODIC TABLE




By about 1915, detailed models of atomic structure had
been developed.
Amazingly, Mendeleev’s Periodic Table was also able to
reflect atomic structure as well as atomic mass and
physical and chemical properties.
As it turns out, atomic structure is the basis for
periodicity in the periodic table and so Mendeleev’s
table had to be slightly reorganized. This time, the focus
was on atomic structure rather than on atomic mass.
The modern periodic table is based on atomic number
and this number is unique to each element.
THE MODERN PERIODIC TABLE
GROUPS OF ELEMENTS

Group 1A - The Alkali
Metals

These elements are all
very reactive metals.
GROUPS OF ELEMENTS

Group 2A - The Alkaline
Earth Metals

Elements in this group
are also reactive metals
but less so than the
alkali metals.
GROUPS OF ELEMENTS

Group 7A - Halogens

These elements react
vigorously with many
things. Even the least
reactive halogens are
extremely corrosive and
harmful.
GROUPS OF ELEMENTS

Group 8A - Noble Gases

The noble gases are
named as such because
they are so unreactive.
They rarely combine to
form compounds and,
when they do, they
quickly decompose back
into single atoms.
Is the atom really the smallest form of matter?
ATOMIC STRUCTURE
FROM PARTICLE THEORY TO ATOMIC THEORY
In the early 1800s, a British schoolteacher
named John Dalton suggested a new way to
distinguish between different elements and
compounds.
 He began experimenting with different gases
and liquids to study their chemical changes.
From his experimental results, he developed
what is now known as Dalton’s atomic theory.

DALTON’S ATOMIC THEORY




1. All matter is made up of small particles called
atoms.
2. Atoms cannot be created, destroyed, or divided into
smaller particles.
3. All atoms of the same element are identical in mass
and size. The atoms of one element are different in
mass and size from the atoms of other elements.
4. Compounds are created when atoms of different
elements link together in definite proportions.
ATOMIC STRUCTURE
According to John Dalton, the smallest form of
matter was the atom.
 An atom was, by definition, meant to be
indivisible.



The word atom comes from the Greek word for indivisible or
uncuttable.
Towards the end of the 19th century, this belief
started to change.
WHAT HAPPENED?


First, scientists like
Heinrich Geissler
developed technology
that allowed electricity to
flow through tubes with
very little air.
These tubes came to be
known as Cathode Ray
Tubes.
DISCOVERING THE ELECTRON


When using Cathode Ray
Tubes (with different
metal cathodes),
scientists began to notice
that the positive end
(anode) glowed when
pressure inside the tube
was lowered.
As a result, scientists
were led to believe that
the glow was produced
when the glass is struck
with some kind of ray
coming from the cathode.
DISCOVERING THE ELECTRON



Eventually scientists
learned that the Cathode
Rays were, in fact,
particles.
J.J. Thomson furthered
the research by showing
that these particles were
negative.
Rather than calling them
cathode rays, scientists
settled on the name
electrons.
J.J. THOMSON’S INFERENCES



Thomson knew that
atoms had no charge
but he also knew that
electrons must be a
part of atoms.
What was missing?
Thomson proposed that
atoms also contain
protons.

Thomson’s Inferences:




Atoms contain both
protons and electrons.
All protons are the same
and all electrons are the
same. They are different
from each other, however.
Electrons are negative
and protons are positive
but there charges are
equal.
A proton is considerably
more massive than an
electron.
THE PLUM PUDDING MODEL


As it turns out, the atom
is divisible; it is made
up of tiny subatomic
particles (protons and
electrons).
Thomson thought that
the atom would appear
something like a raisin
bun.
X-RAYS


While other scientists
were busy figuring out the
components of the atom,
Wilhelm Konrad Röntgen
accidentally used Cathode
Ray Tubes to discover Xrays.
As some of you are
probably keenly aware,
modern medicine would
be very different without
X-rays.
RADIOACTIVITY


As a result of Röntgen’s
work, Henri Becquerel
decided to see if sunlight
gave off X-rays too.
He tested his hypothesis
by placing samples of
crystals (some containing
uranium) on fully wrapped
photographic plates and
then he placed them in
the Sun.



This testing, in the end,
didn’t matter.
On a cloudy day, he placed
the crystals and the
photographic plates in a
dark drawer.
Becquerel was obviously
surprised when he found
that the films were
exposed even in complete
darkness.
RADIOACTIVITY


Clearly, some new selfgenerated rays were
coming from the
uranium bearing
samples.
Marie Curie took a great
interest in this discovery
and she coined the term
radioactivity to describe
the emission of these
new rays.
ERNEST RUTHERFORD

As a result of Madame
Curie’s research, the Kiwi
scientist Ernest Rutherford
performed many
experiments and he
eventually discovered that
radioactivity included three
types of radiation:

Alpha particles (a)

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Beta particles (b)



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Made of matter
4x the mass of 1 proton
Same positive charge as 2
protons
Made of matter
Same mass as 1 electron
Same negative charge as one
electron
Gamma rays (g)



Made of energy
No mass
No charge
RUTHERFORD’S GOLD FOIL EXPERIMENT
Using his knowledge of radiation and the
particles involved, Rutherford designed an
experiment to probe the atom.
 He used alpha particles as “atomic bullets.”
 The alpha particles were shot from a polonium
source towards a thin strip of gold foil.

WHAT ABOUT THE MISSING MASS?
Rutherford’s experiment also led to an
unexpected discovery; Gold has 79 protons in
its nucleus but their total mass accounts for
less than half of the mass of the nucleus.
 Something was missing…
 Rutherford correctly inferred that the nucleus
must contain additional, uncharged particles.
 These particles came to be known as neutrons.

THE BOHR-RUTHERFORD MODEL

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As we already know,
opposites attract.
Therefore, why weren’t
the electrons crashing
into the positive nucleus?
Niels Bohr reasoned that
electrons don’t crash into
the nucleus because they
revolve at just the right
speeds to remain in
distinct orbits around the
nucleus.
THE BOHR-RUTHERFORD MODEL


These electron orbits
came to be known as
electron shells.
Bohr concluded that
given electrons are in
particular shells based
on how much energy
they possessed.
BOHR MODEL OF A NITROGEN ATOM
OTHER BOHR DIAGRAMS
ATOMIC NUMBER
The number of protons in the nucleus of an
atom is the atomic number.
 The atomic number is what identifies an atom
as a specific element.

 Ex:
If the atomic number of an atom is 6, the
element must be carbon.
ATOMIC MASS NUMBER
The sum of the number of protons and the
number of neutrons in an atom is called the
mass number.
 The mass number is always a whole number.

CHEMICAL SYMBOLS
C
12
6
Mass Number
Chemical Symbol
Atomic Number
CALCULATING THE NUMBER OF SUBATOMIC
PARTICLES
Atomic Number = Number of protons
 Mass Number = Number of protons + number
of neutrons
 Number of neutrons = Mass number – number
of protons
 Number of protons = Number of electrons (in a
neutral atom)

PROTONS, ELECTRONS AND NEUTRONS

What happens when you change the number of
protons in an atom?
 If
the number of protons changes, the atomic
number changes and you have a different element.
 This is not an easy thing to do!
ISOTOPES
What happens when you lose or gain neutrons
in an atom?
 Many elements have atoms that exist with
varying numbers of neutrons within their nuclei.
 Isotopes: Forms of an element that have the
same number of protons but different numbers
of neutrons.

ISOTOPES OF HYDROGEN
DEUTERIUM


Deuterium is a major
component in Canada’s
CANDU Nuclear
Reactors.
These reactors use
heavy water (water
containing deuterium)
as a way to transfer
heat energy from the
radioactive uranium to
the steam generators.
CARBON-14 DATING
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Carbon also has a
number of isotopes.
By far the most
common isotope is
carbon-12.
Carbon-14 is slightly
radioactive and it can
be used to determine
the age of organic
(carbon-based) remains.
CARBON-14 DATING



Living tissues are
constantly ingesting
small amounts of
carbon-14.
When an organism dies,
however, carbon-14 is
no longer incorporated
into the tissues.
It then starts to undergo
radioactive decay.
CARBON-14 DATING
Not this half-life!


Carbon-14 has a halflife of about 5730 years.
Scientists can
determine the age of
organic remains based
on how much carbon-14
is remaining in the
tissues.
THE SHROUD OF TURIN


The shroud is a linen cloth
that many believe is the
burial cloth placed over the
body of Jesus of Nazareth
during his burial.
Carbon-14 dating was
performed on pieces of the
shroud and it was
determined that it was
likely made in the Middle
Ages.
THE SHROUD OF TURIN
IONS
We now know what happens when an atom
gains or loses protons or neutrons but does
anything change when an atom gains or loses
electrons?
 Ions are formed when an atom gains (anion) or
loses (cation) electrons.
 Ions are often used to form compounds.
