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By Ms. Buicke
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Syllabus
OC48
Describe the general properties of the alkali metals and understand that
alkali metals are in Group I of the Periodic Table and have similar properties
OC49
Describe the reactions of the alkali metals with air and water (word
equations for reaction with water)
OC50
Understand that Group II elements are the alkaline earth metals
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What is the periodic table?
All of the elements discovered to the present
time are listed in a table called the periodic
table of the elements. if the substance is listed
there it is an element, if it is not listed there it is
not an element!
If you examine the periodic table you will see
that each element has its own symbol. The
symbols for the elements form an international
language. The symbol is a short handed way to
represent the element.
Note: we must know the first 20 elements and
3 table!
there symbols in the periodic
A Russian chemist named Mendeleev arranged
the elements in order of increasing mass of the
atoms of each element. He also lined up
elements that behaved similarly. Only about
half of the elements had been discovered by
this time. Mendeleev left gaps in his table for
elements that had yet to be discovered
Portrait of
Mendeleev
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The modern periodic table has no gaps. The elements
are not arranged according to atomic mass but rather
by atomic number. Elements which have similar
chemical properties
Are placed in columns called groups.
The periodic table is an arrangement of elements in
order of increasing atomic number.
Groups: vertical columns of elements
Periods: horizontal rows of elements in the periodic
table
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Groups:
In the periodic table elements with similar
properties are arranged under one another in
vertical columns called groups. There are eight
main groups. All elements in the same group
have the same number of electrons in their
outer orbit or shell. It is these electrons which
determine the chemical properties of the
elements.
Periods:
The horizontal rows of elements are called
periods there are seven periods in the periodic
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Group I alkali metals
Potassium
K
Lithium
Li
Sodium
Na
Alkali
metals
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Group I alkali metals:
have one electron in their outer shell. The atoms are
keen to get rid of this loose electron. As a result they
are very REACTIVE and behave similarly.
Elements in this group include:
Lithium – Li
Sodium – Na
Potassium – K
Alkali metals are not found freely in nature. They are
not found lying in the earth like gold
They are so reactive they quickly form compounds
Compound: two or more elements chemically
combined.
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The alkali metals must always be stored under
oil this prevents them from reacting with
Moisture in the air.
Physical properties of the alkali metals
• Soft and easily cut
• Low melting points
• Low density ( float in water)
• Shiny when cut but quickly loose their shine
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Alkali earth metals group 1
Potassium
metal
Lithium metal
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Sodium metal
Chemical properties of alkali metals.
There are two chemical properties of alkali metals
which we must know.
Reactions of alkali metals with air:
All of the alkali metals loose their shiny appearance
when exposed to air. We say that they tarnish in air. The
alkali metals react with the oxygen in the air forming a
metal oxide
Lithium + oxygen = lithium oxide
Sodium + oxygen = sodium oxide
Potassium + oxygen = potassium oxide
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Reactions of alkali metals with water:
When a small piece of sodium is added to water
the metal floats on the surface of the water and
melts into a ball, it fizzes around and burns,
sparks, flames and my even explode.
Hydrogen gas is released and sodium hydroxide
is formed which dissolves in the water.
Sodium + water -------> sodium hydroxide +
hydrogen
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When potassium is added to water a similar
reaction occurs.
Potassium + water  potassium hydroxide +
hydrogen.
The least reactive of the alkali metals is lithium
this reacts slowly to form lithium hydroxide and
hydrogen
Lithium + water  lithium hydroxide + hydrogen
The alkali metals react vigorously with
water. Hydrogen gas is given off and a
hydroxide compound is formed.
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Reactivity increases as we go down the
group of metals in group 1. Therefore
Potassium is more reactive then
sodium, sodium is more reactive then
lithium. Why is this the case? discuss
this with your partner.
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Uses of alkali metals:
Sodium is used in street lights.
Lithium is used in batteries.
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Alkali earth metals group II
Beryllium – Be
Magnesium – Mg
Calcium – Ca
All elements in this group have two electrons in their
outer shell. Therefore they need to lose 2 electrons.
Group II elements are not as reactive as group I
elements. The alkaline earth metals don’t have to be
stored under oil, as they are not as reactive with
oxygen or water.
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Calcium 2,8,8,2
Beryllium 2,2
Group II alkali earth metals.
Calcium
Ca
Beryllium
Be
Magnesium
Mg
Alkali
earth
metals
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The alkaline earth metals group II
Beryllium metal
Calcium metal
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Magnesium metal
Exam questions:
2012 HL
Describe the reaction of a named alkali metal with
water and name a product of the reaction.
2012 OL
Calcium is a member of the Group II elements in the
Periodic Table.
(i) What name is given to the Group II elements?
______________________________ metals
2011 HL
The diagram is an outline periodic table. One area, a
group of elements, is shaded. Name this group of
elements and give one chemical property that they have
in common.
Group _________________________
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Property_________________________
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http://www.youtube.com/watch?v=uixxJtJPVXk
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