Metals and Nonmetals. Both of them
 
have physical properties as well as
 
chemical properties. Now we already know
 
how metals and nonmetals differ from
 
each other according to their physical
 
properties. Now let us know how metals
 
and nonmetals are different from each
 
other according to the chemical
 
properties.
 
Keep calm and love oxygen. So let us
 
begin seeing how metals and nonmetals react
 
with oxygen. But the reaction depends
 
upon the reactivity of the metal.
 
Generally we write down the reaction of
 
oxygen with metals as: Metals plus Oxygen
 
gives metal-oxides. Recall the reactivity
 
series, which metals do you see at the
 
top of the series? They are, Potassium
 
and Sodium. Potassium and Sodium react
 
very vigorously with oxygen that too at
 
room temperature and they catch fire. So
 
they are very very reactive. Let's write
 
down the reaction with oxygen using an
 
equation. Potassium that is K reacts
 
with oxygen plus O2. It forms
 
metal oxide that is potassium oxide.
 
The formula of Potassium oxide is
 
K2O, because potassium's valency is one and
 
oxygen's valency is two. Now let's
 
write down the equation for sodium.
 
Sodium is Na, it reacts with oxygen plus
 
O2, and it gives sodium oxide which is
 
Na2O. Now let's talk about calcium
 
and magnesium which lie below potassium
 
and sodium. Now because they are less
 
reactive, to see immediately reaction of
 
calcium and magnesium with oxygen, we need to
 
slightly heat them. So calcium reacts
 
with oxygen on slight heating it gives
 
calcium oxide and what will be the
 
formula of calcium oxide? CaO, because
 
Calcium's valency is two and oxygen
 
valancy is also 2.
 
Let's come to Magnesium. When magnesium
 
reacts with oxygen it forms Magnesium Oxide
 
which is MgO. Now let's go
 
more below the reactivity series andpick
 
aluminum and zinc. Aluminum and zinc are
 
less reactive, so to see their immediate
 
reaction with oxygen we need to strongly
 
heat them. So when aluminum reacts with
 
oxygen it forms aluminium oxide and the
 
formula of Aluminum Oxide becomes Al2O3
 
because aluminium's valancy is three and
 
oxygen's valency is two. Similarly, if we go
 
to see zinc, zinc will react with oxygen
 
on strong heating and form zinc oxide,
 
which is ZnO. Now let's come to Iron. Iron does not
 
burn easily even on strong heating so we
 
take iron filings. They burn
 
vigorously in the presence of oxygen.
 
When we take iron filings, what will be
 
the product form, Iron oxide? Yes, but
 
which Iron Oxide? We know that Iron has
 
2 valencies, two and three. If Iron
 
valancy is considered to be 2 and oxygen's
 
valency  is also two, so the product we
 
should get is FeO and if Iron's valency is
 
considered to be three and oxygens valency
 
as is 2 the product we shall get is
 
Fe2O3. But the product we
 
will get here is the combination of
 
these two, so when you add FeO and Fe2O3
 
we get Fe3O4. So the product when Iron
 
filings are burn with oxygen is Fe3O4
 
Now we know that if we consider FeO,
 
FeO is nothing but Iron(II)Oxide where Iron's
 
valency is 2 and if we consider Fe2O3,
 
The valency here of Iron is three so it is
 
known as iron(III) oxide. But what about Fe3O4,
 
which is a combination of iron's valency
 
2 as well as iron's valency 3?
 
For that the name becomes Iron(II, III)
 
oxide so remember when Iron
 
filings burn, they give Fe3O4
 
which is Iron(II, III) oxide.
 
Now let us come to copper. Now copper does
 
not burn on strong heating but a small
 
layer of copper oxide is formed on the
 
rod. So copper that is Cu plus oxygen gives
 
copper oxide which is CuO. Here
 
copper's valency is 2 and oxygen's valency
 
is also 2. So finally we see
 
metal plus oxygen gives metal-oxide. Now
 
I wonder what is the nature of these
 
metal oxides? For that let us dissolve them
 
in water.
 
Ok we have four beakers. In the first
 
beaker, we have dissolved Potassium
 
Oxide. In the second beaker we have
 
dissolved sodium oxide. In the third we
 
have magnesium oxide dissolved in water and
 
in the fourth because we have calcium
 
oxide dissolved in water. Now let's test
 
all the four solution with a litmus
 
paper. We take a red litmus paper and we
 
dip in the four solutions, we find out
 
that red litmus paper has turned blue when
 
red turns blue that means the solution
 
is basic in nature. So generally we find
 
that metal oxides are basic in nature.
 
But there are certain metal oxide which
 
are amphoteric in nature.
 
What do you mean by amphoteric. Okay
 
metal oxide which are basic as well as
 
acidic are called amphoteric oxides.
 
For example aluminum oxide and zinc
 
oxide, both of them react with acid and
 
give salt and water and they also react
 
with bases to give salt and water. That
 
means when they come in contact with
 
an acid they behave like bases and
 
when they come in contact with the base
 
they behave like an acid. Let's consider
 
aluminium oxide.
 
When aluminium oxide reacts with sodium
 
hydroxide, that is a base, it forms a
 
salt sodium aluminate. Sodium is Na,
 
aluminate is AlO2. Both their
 
valencies are 1,so the formula is NaAlO2
 
and they form water that is H2O .Then if aluminum
 
oxide reacts with HCl, again it forms salt and
 
water. It forms aluminium chloride and
 
H2O. In the first case aluminium oxide is
 
behaving like an acid and in the second
 
case it is behaving like a base. So this
 
is what we call an amphoteric oxide.
 
Now what would have happened when we
 
dissolve the metal oxide in water, so
 
that they have turned the red litmus blue?
 
Well whenever you dissolve a metal oxide
 
in water and it is soluble, it forms a
 
base that is an alkali. When
 
potassium oxide dissolves in water, it
 
forms potassium hydroxide and sodium
 
oxide dissolves in water forms sodium
 
hydroxide. When magnesium oxide dissolves in
 
water it forms magnesium hydroxide and
 
when calcium oxide dissolves in water
 
forms calcium hydroxide. Now let's see
 
how non metals react with oxygen.
 
When nonmetals react with oxygen,
 
they form non metal oxide. For example the
 
nonmetal carbon, carbon reacts with
 
oxygen to form carbon dioxide CO2. This
 
can be seen during burning of coal. When
 
coal burns it forms carbon dioxide. Let's
 
see one more non-metal, that's sulphur.
 
When we take sulphur powder in a spatula
 
and heat it, it forms sulphur dioxide gas.
 
We collect this gas in a test tube. Now let's
 
test this gas, let's see whether it is
 
acidic or basic. For that we use a litmus
 
paper. We're using blue litmus paper here,
 
the dry blue litmus paper. When dry blue
 
litmus paper comes in contact with SO2,
 
we will see no change but if we take a
 
moist blue litmus paper we will see that
 
the litmus paper is changing from blue
 
to red.
 
This indicates that sulphur dioxide gas is
 
acidic. But why didn't show any change on
 
the dry litmus paper? Recall, acid
 
properties are seen only in the presence
 
of water.
 
Ok, now this indicates that sulphur
 
dioxide is acidic.
 
Let's take carbon dioxide, if we test
 
carbon dioxide we find the same thing,
 
the blue litmus changes red. That means
 
even carbon dioxide is acidic. So generally
 
we say nonmetal oxide and acidic in
 
nature. Now what must be happening when
 
non metal oxide come in contact with
 
water? When CO2 comes in contact with
 
water, it forms an acid, carbonic acid, that is
 
H2CO3 and when sulphur dioxide, that is
 
SO2 comes in contact with water, it forms
 
sulphurous acid that is H2SO3. Due
 
to which when these gases come in
 
contact with moist litmus paper, which is
 
which has water in it, they form acid
 
and they turn the litmus paper from
 
blue to red but there are certain
 
nonmetal oxides like carbon monoxide,
 
nitrogen monoxide, dinitrogen oxide, water
 
all these are neutral oxides. So we
 
can state that generally non metal
 
oxides are acidic in nature except carbon
 
monoxide, nitrogen monoxide, dinitrogen
 
oxide, water etc. Now this N2O
 
your information is also known as
 
laughing gas.
