in this lesson we will learn about the
alkaline earth metals in group 2 of the
periodic table we will focus on
magnesium and calcium and learn about
how they react with oxygen and water and
the products formed from these reactions
the alkaline earth metals are beryllium
magnesium calcium strontium barium and
radium located in group 2 of the
periodic table these metals all have two
electrons in their valence shell and
with the exception of beryllium can lose
these valence electrons to form an ion
with a +2 charge like the alkali metals
these metals except for magnesium are
stored in oil similar properties and
reactivity trends are also observed
moving down the group their density and
reactivity increases melting points and
boiling points decrease and the metals
become softer we will now learn about
the reactions of magnesium and calcium
with oxygen and water magnesium is shiny
and silver but you will see that your
magnesium strip may be dull this is due
to the formation of an oxide layer from
exposure to air simply clean it with
steel wool so to remove as much of the
oxide layer as possible using a pair of
tongs take the magnesium strip and hold
it to a roaring Bunsen burner flame the
combustion of magnesium proceeds with a
bright white flash take care not to look
at this flash magnesium reacts with
oxygen to produce magnesium oxide which
is a white solid here is a challenge do
you expect calcium to be softer or
harder than magnesium please pause the
lesson to think about this and resume
when you are ready
calcium is softer than magnesium moving
down the group the metals become softer
overall though these metals are harder
than the alkali metals calcium is also
shiny and silver using a pair of
tweezers take out a chunk and cut a
small piece using a scalpel remove
excess oil using paper towels using
tongs place in a roaring Bunsen burner
flame you will observe that it burns
with a red flame calcium reacts with
oxygen to produce calcium oxide which is
a white solid so magnesium and calcium
react with oxygen to form their
respective oxides let the formed calcium
oxide cool it's important that you allow
it to cool sufficiently because the next
step is exothermic place the cooled
calcium oxide in cold water calcium
oxide reacts with water to produce a
solution of calcium hydroxide also known
as lime water you will see a white
precipitate at the bottom of the beaker
once everything settles this is solid
calcium hydroxide as it is only slightly
soluble in water magnesium will only
react with steam not cold water the
reaction from steam forms magnesium
oxide and hydrogen gas in this practical
it is imperative that the magnesium
strip is heated not the mineral wool
soaked in water hydrogen gas can be
collected over water untested to confirm
its presence how do you think the
reaction of calcium with water compares
to the reaction of magnesium with water
please pause the lesson to think about
this and resume when you are done three
action of calcium with water is expected
to be more vigorous as the reactivity of
these metals increases moving down the
group calcium reacts with cold water to
form calcium hydroxide and hydrogen gas
note that calcium sinks to the bottom
in this reaction the effervescence shows
that a gas is being produced in summary
the alkaline earth metals are the group
two metals they exhibit similar
properties and reactivity trends to the
alkali metals magnesium and calcium
react with oxygen to form their
respective oxides magnesium reacts with
steam to produce magnesium oxide and
hydrogen gas calcium reacts with cold
water to produce calcium hydroxide and
hydrogen gas