DK - WOW! The Visual Encyclopedia of Everything

Everything in the world is made from

elements – pure substances that cannot

be broken down into anything simpler.

Elements can be grouped according to

the properties they have in common,

such as their appearance, how they

conduct electricity, and how they react

with other substances. There are nine

main groups and the element hydrogen,

which is unique.

Elements technology

90

(^1) HYDROGEN
Hydrogen makes up 90 per
cent of all the matter in the
Universe. Pure hydrogen is
an invisible gas on Earth. It
is not considered part of any
one group. Hydrogen powers
the nuclear reactions inside
stars, including our Sun, and
is found on Earth in the
compound H 2 O, or water.
(^2) ALKALINE-EARTH
METALS
Alkaline-earth metals react
with water and are found
in minerals in Earth’s
crust. In pure form, they
are silvery-white. They are
similar to alkali metals, but
less reactive. Calcium, found
in chalk, milk, and bones,
is a member of this group.
(^3) ALKALI METALS
Sodium, contained in salt,
is an alkali metal. These
elements are characterized
by their vigorous reaction
with water. On contact, they
will zoom all over the water’s
surface or even explode. Alkali
metals are not found in a pure
form in nature because they
react so strongly with water.
(^4) TRANSITION
METALS
This group is the largest
and includes iron, silver,
gold, nickel, platinum, and
titanium. Transition metals
are considered typical
metals – they are hard and
shiny, conduct electricity
and heat well, and have
high melting points.
(^5) ACTINIDES
The elements in this group
are radioactive metals
mostly created synthetically
in nuclear reactors or
nuclear explosions. They
have unstable atoms
that break up and give
out radiation particles.
Uranium and plutonium
are examples of actinides.
Copper is a good
conductor of heat

Electricity

Potassium is an

alkali metal found

in minerals in

Earth’s crust

Radioactive sign

is used to show

elements that

emit radiation

Magnesium is a silvery

substance that burns with

a dazzling white flame

The Orion Nebula, a

vast cloud of gas and dust,

is made mainly of hydrogen

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