The Periodic Table
The Ultimate Cheat-Sheet
Elementary My Dear Watson….



Elements are distinguished by
the number of protons
Each element has unique
properties
How are they arranged? Is
there a pattern?
The “Original”
Why Do We Need a Periodic Table?




By 1700, only 13 elements were known
The rate of discovery increased in the
18th century (Davy, Lavoisier, Priestly)
But how could scientists know an
element was “new?”
Chemists needed a way to organize the
elements
How Was It Developed?
 In
1829, Dobereiner published a
classification system using triads
 Triads are
groups of 3 elements with
similar properties
 But, not all elements could be grouped
into triads
Lothar Meyer




In 1864, Lothar Meyer published an early
version of the periodic table
It contained 28 elements classified into 6
families by their valence (combining power)
This was the first time that elements had been
grouped and ordered according to their
valence.
Work on organizing the elements by atomic
weight had hitherto been stymied by inaccurate
measurements of the atomic weights.
7
de Chancourtois



One of the first to notice periodicity
In 1862 developed a cylindrical design
Ignored due to “geological terms”
How Was It Developed….
 In
1865, Newlands classified elements
into 11 groups
 Noticed that many groups differed by
 He
called this his “Law of Octaves”
“8”
Development


Other systems were explored…
In 1869, Dmitri Mendeleev proposed
his periodic table
He played
“chemical
solitaire” on the
train
 There were 60
elements to
organize

1834-1907
How Did Mendeleev Do It?



He organized the elements by increasing
atomic mass and “combining power”
He left a space in his table if an element
was unknown
In time, those spaces were filled in with
elements that matched his predictions
Elements’ Properties are Predicted
Property
Mendeleev’s Predictions in 1871
Observed Properties
Scandium (Discovered in 1877)
Molar Mass
Oxide formula
Density of oxide
Solubility of oxide
44 g
M2O3
3.5 g / ml
Dissolves in acids
43.7 g
Sc2O3
3.86 g / ml
Dissolves in acids
Gallium (Discovered in 1875)
Molar mass
Density of metal
Melting temperature
Oxide formula
Solubility of oxide
68 g
6.0 g / ml
Low
M2O3
Dissolves in ammonia solution
69.4 g
5.96 g / ml
30 0C
Ga2O3
Dissolves in ammonia
Germanium (Discovered in 1886)
Molar mass
Density of metal
Color of metal
Melting temperature
Oxide formula
Density of oxide
Chloride formula
Density of chloride
Boiling temperature
of chloride
72 g
5.5 g / ml
Dark gray
High
MO2
4.7 g / ml
MCl4
1.9 g / ml
Below 100 oC
O’Connor Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles 1982, page 119,
71.9 g
5.47 g / ml
Grayish, white
900 0C
GeO2
4.70 g / ml
GeCl4
1.89 g / ml
86 0C
Mendeleev


Some people consider Meyer and Mendeleev
the co-creators of the periodic table
Most agree that Mendeleev's accurate
prediction of the qualities of what he called
eka-silicon (germanium), eka-aluminium
(gallium) and eka-boron (scandium) qualifies
him for deserving the majority of the credit for
studies
14


Mendeleev did not know the
structure of atoms and that the
number of protons was unique for
each element
Now the periodic table is arranged
by increasing atomic number
The Modern Periodic Table



Is an organized display of
elements
Is arranged so that elements
with similar properties fall into
the same group
Is used to predict the
behavior of elements
The “Noble Gases” don’t easily
react with other elements.
Rows of the Periodic Table


Rows of the PT are called
“periods.”
All of the elements in a period
have the same number of
energy levels for their valence
(s & p) electrons
Periods (cont.)

Elements close to each other in the
same period are more similar than
those further away.
K and Ca are
similar
K and Kr are
very different
So…


Properties of the elements within a
period change as we move across a
period from left to right
The pattern of properties within a
period repeats as we move from one
period to the next
The Periodic Law
When elements are arranged in order
of increasing atomic number, there is a
periodic repetition of their physical and
chemical properties
Regions of the PT
1) Metals
The largest region of the PT ~ 80%
Properties of Metals


Excellent conductors of heat and
electricity
Usually lustrous, ductile, and
malleable.
Sodium metal
Copper wire
Gold charm
2) Nonmetals
The second largest region of the PT
Properties of Nonmetals


Poor conductors of heat and
electricity
Most are gases or brittle solids at
room temperature.
Graphite
Diamond
Chlorine gas
3) Metalloids



Have some properties of metals and
some of nonmetals
Silicon is useful in computers because
they conduct electricity “moderately”
Semi-conductors
Other Uses of Metalloids





Lasers
Infrared sensors
Alloys
Glass products
Added Impurities
The Elements at the Bottom


These are the lanthanides and actinides
Glenn Seaborg “moved” these
Special Groups of Elements

Group 1A – the Alkali Metals




The name alkali comes from the Arabic
al aqali, meaning “the ashes.”
Wood ashes are rich in compounds
containing sodium and potassium
Group 2A – the Alkaline Earth Metals
Group 7A – the Halogens

Literally means “salt former”
30
The Representative Elements


These are the elements in Groups 1A – 7A
They represent a wide range of properties



Metals, nonmetals, and metalloids
Solids, liquid (Br), and gases
The highest level s & p orbitals are NOT
filled
31
Examples

Electron configurations for Group 1A

Electron configurations for Group 4A
32
Group Number and e- Number
For any representative element, its group
number equals the number of electrons in the
highest occupied energy level (valence
electrons).
Group 1A
Group 4A
33
Noble Gases



NOT considered representative
elements
Unreactive
Uses:
Krypton is mixed with Argon in fluorescent
lights (also to render Superman inert)
Neon is used for signs
Helium is used in weather and
toy balloons
What About The “Ones in the Middle”


These have different letter
designations, depending on the
table
These are also called


Transition metals
Inner transition metals
35
Transition Metals


The highest occupied s sublevel and a
nearby d sublevel contain electrons
These elements are also called d -block
elements
36
The Inner Transition Metals


AKA: the lanthanides and actinides.
The highest occupied s sublevel and a
nearby f sublevel generally contain
electrons.
37
f-orbitals
38
Blocks of Elements
39
Rare Earth Elements


Scandium, Yttrium, Lanthanum, and
Cerium through Lutetium
Used in electronics



Thulium (Tm) – lasers & x-rays
Neodymium (Nd) - magnets
Not rare – hard to separate


Elements very similar
Charges are 3+
40
The Racetrack Design