Page 51 - Science Class 07
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ELEMENTS v Metals are malleable, i.e., they can be
An element is the simplest form of a pure beaten into sheets.
substance. All substances are ul mately made v Most of the metals are duc le, i.e., they
up of elements. Now, we can define elements can be drawn into thin wire.
as the simplest form of ma er which cannot be v Metals are the good conductors of heat as
decomposed by any chemical means into well as electricity.
simpler substances nor it can be formed by the
combina on of other substances. Some
common examples of elements are hydrogen,
oxygen, nitrogen, iron, gold, copper, mercury Metals are not found in the free state in the
carbon, etc. earth’s crust. They are found in nature in
There are 115 elements known to us so far. Out combined states. The natural materials in
of these, 106 elements occur naturally while which metals occur in the earth are called
the other elements are developed by man. minerals.
These elements can be further divided into NON-METALS
metals, non-metals and metalloids. From these
elements, all the other substances on the earth Non-metals are those which lack all the
are made. That’s why the elements are called metallic a ributes. They are good insulators of
the building blocks of the universe. heat and electricity. They are mostly gases and
some mes liquid. Some of them are even solid
METALS
at room temperature like, carbon, sulphur and
A metal is a material (an element, compound, or phosphorus.
alloy) that is typically hard, opaque, shiny, and
There are about 22 non-metals out of which 11
has good electrical and thermal conduc vity.
are gases (e.g., oxygen, nitrogen and chlorine)
Metals are generally malleable, that is, they can
one liquid (bromine) and remaining 10 are
be hammered or pressed permanently out of
solids (e.g., carbon, sulphur, phosphorous and
shape without breaking or cracking as well as
iodine).
fusible and duc le.
Following are the physical proper es of non-
Metals have these physical proper es:
metals:
v All metals are solid except mercury which is
v Non-metals are bri le in nature. They
a liquid.
cannot be beaten into sheets.
v Metals have high boiling and mel ng
v They do not posses lustre and cannot be
points. polished.
v They are generally bad conductors of heat
and electricity. Only graphite is a non-metal
which is also a good conductor of electricity.
METALLOIDS
A metalloid is a chemical element that exhibits
some proper es of metals and some of
Metals
Science-7 51
