Reading the Periodic Table
Review – Current Atomic Model
Protons
Electron
cloud
nucleus
Neutrons
Electron
Introduction
There are 118 known elements in the universe.
The periodic table organizes all of the
elements in a way that is understandable and
useful.
REMEMBER!
Elements differ by the
number of protons (#p)
each has in its nucleus.
Introduction
The current periodic table has 118 squares.
Each square shows the elements name,
symbol, atomic number and atomic mass.
Information in Each Square
Take the element Helium, for example:
CHEMICAL
SYMBOL
ELEMENT
NAME
ATOMIC
NUMBER
(p) or (e)
ATOMIC
MASS
(p + n)
Example – 1 Atom of Helium
(p) or (e)
(2p + 2n)
Atomic Math
Calculate the # of protons, electrons & neutrons.
p = _____
p = _____
p = _____
e = _____
e = _____
e = _____
n = _____
n = _____
n = _____
Atomic Math
Calculate the # of protons, electrons & neutrons.
p=3
p = 11
p = 30
e=3
e = 11
e = 30
n=4
n = 12
n = 35
Something Strange
There’s something strange about mass numbers.
Mass numbers are not
whole numbers, but are
decimals instead.
How can you have a
decimal proton or neutron?
This can be explained by isotopes.
What are Isotopes?
Every atom of each element has the same #
of protons, but the # of neutrons can change.
Isotopes are elements with the same # of
protons but a different # of neutrons.
This gives each
isotope a different
mass number
(p+n)
Example 1
There are 3 natural isotopes of carbon.
6 NEUTRONS
7 NEUTRONS
8 NEUTRONS
Each isotope has 6 protons; they are all carbon!
How many neutrons does each isotope have?
Example 2
There are 3 natural isotopes of oxygen
7 NEUTRONS
8 NEUTRONS
10 NEUTRONS
Each isotope has 8 protons; they are all oxygen!
How many neutrons does each isotope have?
Why Decimals?
In the universe, the C-12 isotope is much
more abundant than C-13 and C-14 isotopes.
Atomic mass is
a weighted
average of all
of an elements
natural
isotopes.
A weighted average takes into account each
isotope’s mass and its natural abundance (%).
Why Decimals?
In the universe, the C-12 isotope is much
more abundant than C-13 and C-14 isotopes.
Atomic mass is
a weighted
average of all
of an elements
natural
isotopes.
NOTE: The weighted average is always closest to
the mass of the most abundant natural isotope!
Abundance Example 1
The atomic mass number of oxygen is 15.999.
MOST ABUNDANT
What’s the most abundant oxygen isotope?
This is because 15.999 is closest to O-16.
Abundance Example 2
The atomic mass number of chlorine is 35.45.
MOST ABUNDANT
What’s the most abundant chlorine isotope?
This is because 35.45 is closest to Cl-35.
Before the Periodic Table
Before the periodic table was invented,
the field of chemistry was a mess!
The roughly 63 elements were not organized.
It was very difficult to locate
information on all the elements
and to predict how elements
would react with each other.
Dmitri Mendeleev (1869)
Dmitri Mendeleev created the periodic table.
Mendeleev was a chemist and professor who
found a new way to organize the elements.
While writing a textbook, Mendeleev
wanted to find a way to organize the
63 known elements at the time. While
doing this, he made a famous
discovery that ultimately solved the
problem of the disorganized elements.
A Game of Cards
Mendeleev was a fanatical card player, and he
used his talents to solve the element puzzle.
I spent time collecting information
about all of the known elements
and then made cards for them,
similar to a deck of playing cards.
A Game of Cards
Mendeleev was a fanatical card player, and he
used his talents to solve the element puzzle.
On each card I wrote the element’s
name, chemical symbol, atomic
mass, physical and chemical
properties and bonding power.
A Game of Cards
Mendeleev was a fanatical card player, and he
used his talents to solve the element puzzle.
When I placed the elements in
order of increasing atomic mass, I
began to notice clear patterns in
their properties and reactivity...
I placed the first 7 element cards in
a row by increasing atomic mass.
I placed the next 7 in a new row.
Their properties repeated perfectly!
I placed the next 7 in a new row.
Their properties repeated perfectly!
I filled the rest of the table but left
gaps where the pattern didn’t fit.
I claimed that the missing elements
would be found and even
predicted their properties in great
detail.
I could do this since I discovered
that elements in the same vertical
column have similar properties.
Eventually, these elements were
discovered and my predictions
were nearly perfect. Hooray!
Bold Predictions
Dmitri Mendeleev’s table was very accurate.
Mendeleev’s idea was put to the test when
gallium (Ga) was discovered in France in 1875.
A scientist named Paul Emile Lecoq
de Boisbaudran discovered Ga and
published information about the metal.
Mendeleev publicly told the scientist
that his measurements for gallium’s
density were incorrect since it didn’t
match his predictions… and was right!
A Modern Equivalent
Mendeleev took a huge risk when publicly
challenging de Boisbaudran about gallium.
The best way to imagine what Mendeleev did
in 1875 is put it in a modern context.
A TWITTER WAR
After Mendeleev’s Table
Mendeleev’s table was great, but had a few errors.
Once protons were discovered by Rutherford,
Mendeleev’s periodic table was rearranged.
In 1913, British scientist Henry
Moseley reorganized the table by
atomic number (#p), which solved
many issues with Mendeleev’s table;
his table closely resembles today’s.
A New & Improved Table
MOSELY’S
PERIODIC
TABLE
(1913)
MODERN
PERIODIC
TABLE
(NOW)
Periods
HORIZONTAL ROWS ARE CALLED PERIODS.
THERE ARE 7 PERIODS IN TOTAL.
1
2
3
4
5
6
7
ELEMENTS IN SAME PERIOD = SAME # OF ENERGY LEVELS.
Groups
VERTICAL COLUMNS ARE CALLED GROUPS or FAMILIES.
THERE ARE 18 GROUPS IN TOTAL.
1
18
13 14 15 16 17
2
3
4
5
6
7
8
9 10 11 12
ELEMENTS IN SAME GROUP = SAME # ELECTRONS IN OUTER LEVEL.
Groups
ELEMENTS IN THE SAME GROUP HAVE SIMILAR PROPERTIES.
Names of Key Groups
Alkali Metals
Alkaline Earth Metals
Transition Metals
Noble Gases
Halogens
Metals, Nonmetals, Metalloids
METALS ARE FOUND ON THE LEFT. NONMETALS ON THE RIGHT.
THEY ARE SEPARATED BY A ZIGZAG LINE OF METALLOIDS.
metalloids
metals
nonmetals
Metals, Nonmetals, Metalloids
METALS
METALLOIDS
NONMETALS
Shiny
Properties that are in
between metals and
nonmetals
Dull
Some metalloids have
more metallic props
Weak
Hard
Strong
Dense
Good conductors
Malleable
Ductile
e.g. iron, copper
Some metalloids have
more nonmetal props
Example: silicon is a
semiconductor
e.g. silicon,
germanium
Soft
Lightweight
Poor conductors
Brittle
Inelastic
e.g. carbon, nitrogen
Periodic Table Groups
Recall that vertical columns are called groups.
A periodic table group is like a “family”,
where members may look and act similarly.
Elements in the same group
have similar physical and
chemical properties.
Let’s look at 5 key groups…
Group 1 – Alkali Metals
Alkali Metals
1
18
13 14 15 16 17
2
3
4
5
6
7
8
9 10 11 12
Group 1 – Alkali Metals
Very reactive metals
Na
Shiny, silvery, soft
Stored in oil to avoid
reacting with the air
Very low density
Cut with a knife
K
React with water
Li, Na, K, Rb, Cs, Fr
Explosive in H2O
Group 2 – Alkaline Earth Metals
1
Alkaline Earth Metals
18
13 14 15 16 17
2
3
4
5
6
7
8
9 10 11 12
Group 2 – Alkaline Earth Metals
Slightly reactive metals
Ca
Shiny, silvery-white
Common in rocks,
plants, human body
Relatively strong,
malleable and ductile
Be, Mg, Ca, Sr, Ba, Ra
Silvery-white metal
Be
Found in emeralds
Groups 3-12 – Transition Metals
1
18
2
Transition Metals
3
4
5
6
7
8
9 10 11 12
13 14 15 16 17
Groups 3-12 – Transition Metals
Large metal group
Au
Shiny, metallic luster
Hard, dense,
malleable & ductile
Oxides are used in
pigments & paints
e.g. Cu, Al, Zn, Fe, Au
Shiny metallic luster
Fe
Iron oxides
Group 17 – Halogens
Halogens
1
13 14 15 16 17
2
3
4
5
6
7
8
9 10 11 12
18
Group 17 - Halogens
Very reactive
nonmetals
Come in all three
states of matter
Br
Both solid & gas form
Give off colored vapors
Highly toxic; used as
antiseptics & cleaners
F, Cl, Br, I, At
Cl
Poisonous green gas
Group 18 – Noble Gases
Noble Gases
1
18
13 14 15 16 17
2
3
4
5
6
7
8
9 10 11 12
Group 18 – Noble Gases
Unreactive nonmetals
He
Completely “inert”
Odorless, colorless gases
Nonflammable gas
Glow with distinct
colors when electricity
is run through them, as
in “neon” lights
He, Ne, Ar, Kr, Xe, Rn
Gas-discharge lights
Review of Key Groups
Alkali Metals
Noble Gases
Alkaline Earth Metals
Halogens
Transition Metals
metalloids
metals
nonmetals