Dmitri Mendeleev organized the
known elements into a table called the
periodic table.
He organized
them by their
increasing
atomic
masses.
Today we organize the
elements by their
increasing Atomic
Number.
Insert copy of the periodic table.
Rows on the periodic table are called periods.
All the elements listed in a row belong to the
same period. There are 7 (seven) periods.
Columns in the periodic table are called groups
or families. All elements in a group have
similar properties.
Insert copy of the periodic table.
The columns have been given an Arabic number.
The columns are numbered 1 – 18 starting at the
left and moving to the right. Please make sure that
your periodic table has them numbered like this.
Valence Electrons
The outer most energy level is
usually not full or complete .
These electrons in the outer
energy level are called Valence
electrons.
Valence electrons are important
because they determine how an
element will react with other
substance.
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Group 1 and 2 the number of Valence
electrons in the outer energy level will
match the group number.
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Groups 3 through 12 do not follow any
particular rule to determine the number
of Valence electrons.
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Group 13 to 18 – The Valence electrons
for each of these is the group number
less 10. For example Group 14 – 10 = 4
Valence electrons.
Elements whose atoms
gain, lose or share
electrons are reactive and
they combine to form the
many compounds we use
in our daily lives.
Elements are categorized as
metals, nonmetals or
metalloids.
Metals: An element that has
luster, is malleable and ductile,
and is said to be a good
conductor of heat and
electricity.
What is luster, malleable and
ductile?
Luster describes the way a surface reflects
light…therefore metallic luster would be shiny
like a metal object.
Malleable means to be able to press or pound
the substance into sheets or different shapes.
Ductile means that the substance can be
drawn out into thin wires.
Elements are categorized as metals,
nonmetals or metalloids (cont’).
Nonmetals: an element that is
usually a gas or a brittle solid
at room temperature. It is a poor
conductor of heat and
electricity.
Elements are categorized as metals,
nonmetals or metalloids (cont’).
Metalloid: an element that
shares some characteristics or
properties with both metals and
nonmetals.
Group 1 and 2 Elements:
These elements are so
reactive that they are only
found combined with other
elements in nature.
3
Group 1: Alkali Metals
Li
Lithium
6.941
11
Na
Sodium
22.990
19
•Soft – can be cut with a knife
•Shiny and silver colored
•Low Density (some will even float)
K
Potassium
39.098
•Most reactive of the metals
37
Rb
Rubidium
•Valence electrons = 1
85.468
55
Cs
Cesium
•Reacts violently with water
forming a hydrogen gas
132.905
87
Fr
Francium
223.020
•Compounds from these are very
useful such as NaCl
4
Be
Beryllium
9.012
12
Mg
Magnesium
24.305
20
Group 2: Alkaline- Earth Metals
•Very reactive but not as reactive
as Alkali Metals.
•Silver colored
Ca
Calcium
40.078
38
Sr
Strontium
87.62
56
Ba
barium
137.327
88
Ra
Radium
226
•More dense than Group 1 metals
•Valence electrons = 2
•Useful compounds include: Calcium
compounds such as cement, plaster,
chalk, and YOU.
Group 3 to 12: Transition Metals
•Do not lose their valence electrons
as easily as groups 1 & 2.
•Less reactive than Alkali and
Alkaline Earth metals
•Shiny
•Good conductors of electricity
•Higher density and melting points
(except mercury) than Group 1 and 2
Group 3 to 12: Transition Metals (cont’.)
•Lanthanides: The first row underneath
the periodic table: Shiny, reactive,
many are used in the production of
steel.
•Actinides: The second row
underneath the periodic table: These
elements are all radioactive and
unstable..
Note: Elements found after 94 (Plutonium) are man made and not
found in nature
5
B
Boron
10.811
Group 13: Boron Group
•Reactive
13
Al
Aluminum
26.982
31
•Valence electrons = 3
•Contains 1 Metalloid and 4 Metals
Ga
Gallium
69.723
49
In
Indium
114.818
81
Tl
Thallium
204.383
•Solid at room temperature
•Aluminum is the most abundant
in this group and the most common
in the Earth’s crust
6
C
Carbon
12.011
14
Si
Silicon
28.086
Group 14: Carbon Group
•Reactivity varies in this group
depending on the element
•Valence electrons = 4
32
Ge
Germanium
72.64
•This group contains 2 metals, 1
nonmetal and 2 metalloids.
50
Sn
Tin
118.710
82
Pb
Lead
207.2
•Many forms found uncombined
in nature such as diamonds
•Compounds are very useful:
proteins, fats, carbohydrates,
computer chips.
Group 15: Nitrogen Group
7
N
Nitrogen
14.007
15
P
Phosphorous
30.974
33
As
Arsenic
74.922
•Reactivity varies in this group depending
on the element
•Valence electrons = 5
•Group contains 1 metal, 2 Nonmetals, and
2 metalloids
•Phosphorous is very reactive and only
found in nature combined with other
elements.
51
Sb
Antimony
121.760
83
Bi
Bismuth
208.980
•All but nitrogen are solid at room
temperature.
•Nitrogen makes up 78% of our
atmosphere.
•Generally unreactive.
8
O
Oxygen
15.999
16
S
Sulfur
32.065
34
Se
Selenium
78.96
52
Te
Tellurium
127.60
84
Po
Polonium
209
Group 16: Oxygen Group
•More reactive than group 15
•Valence electrons = 6
•Group contains 1 Metals, 3 Nonmetals and 1
Metalloids
•Sulfur is found in nature and is used to make
sulfuric acid, a very commonly used chemical
in industry.
•All but oxygen are solid at room temperature.
•Oxygen makes up 21% of the Earth’s
Atmosphere
•Oxygen is very reactive and combines
with many other elements especially
metals
•Rust is the result of the oxidation of metal.
9
F
Fluorine
18.998
17
Cl
Group 17: Halogen Group
•Very reactive
•Valence electrons = 7
•Nonmetal group
Chlorine
35.453
35
Br
Bromine
79.904
53
I
Iodine
126.904
85
At
Astatine
210
•Poor Conductors of electricity and heat
•React violently with alkali metals to form
salts
•Never found uncombined in nature
•Atoms of these elements only need to
gain 1 electron to fill their outer shell
•Chlorine and Iodine are both in this group
and can be combined to make
disinfectants.
2
He
Helium
4.003
10
Ne
Neon
21.180
18
Ar
Argon
Group 18: Noble Gas Group
•Non-reactant
•Valence electrons = 8
•Outermost energy shell is full
•Colorless, odorless gases at room temp.
39.948
36
Kr
Krypton
83.80
54
Xe
Xenon
131.293
86
Rn
Radon
222
•Under normal conditions they do not react
with other elements
•All found on Earth in very small amounts
•Argon is the most common in the group
•Their non-reactivity makes them very
useful for light bulbs, helium for blimps
and weather balloons.
1
H
Hydrogen
1.008
Hydrogen Stands Alone:
•Properties do not match the properties
of any single group
•Valence Electrons = 1
•Easily looses that one valence electron
•Physical properties are like the
nonmetal group
•Most abundant element in the
Universe
•Its reactive nature makes it useful as a
fuel for rockets.
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