Chemistry Reference
In-Depth Information
Table 2.4
Some common elements and their symbols. The Latin names
of some of the elements are given in brackets.
Cl
Cl
a
As a letter-and-stick model.
Element
Symbol
Physical state at room
temperature and pressure
Aluminium
Al
Solid
Argon
Ar
Gas
Barium
Ba
Solid
Boron
B
Solid
Bromine
Br
Liquid
Calcium
Ca
Solid
Carbon
C
Solid
b
As a space-fi lling model.
Figure 2.5
A chlorine molecule.
Chlorine
Cl
Gas
Chromium
Cr
Solid
Molecules are not always formed by atoms of the
same type joining together. For example, water exists
as molecules containing oxygen and hydrogen atoms.
Copper (Cuprum)
Cu
Solid
Fluorine
F
Gas
Germanium
Ge
Solid
Questions
1
How would you use a similar chemical shorthand to write a
representation of the molecules of iodine and fl uorine?
2
Using the Periodic Table on p. 294 write down the symbols
for the following elements and give their physical states at
room temperature:
a
chromium
Gold (Aurum)
Au
Solid
Helium
He
Gas
Hydrogen
H
Gas
Iodine
I
Solid
Iron (Ferrum)
Fe
Solid
Lead (Plumbum)
Pb
Solid
b
krypton
c
osmium.
Magnesium
Mg
Solid
Mercury (Hydragyrum)
Hg
Liquid
●
Compounds
Compounds are pure substances which are formed when
two or more elements chemically combine together.
Water is a simple compound formed from the elements
hydrogen and oxygen (Figure 2.6). This combining of
the elements can be represented by a word equation:
hydrogen + oxygen → water
Neon
Ne
Gas
Nitrogen
N
Gas
Oxygen
O
Gas
Phosphorus
P
Solid
Potassium (Kalium)
K
Solid
Silicon
Si
Solid
Silver (Argentum)
Ag
Solid
Sodium (Natrium)
Na
Solid
Sulfur
S
Solid
Hydrogen
a pure
element
Oxygen
a pure
element
Hydrogen and
oxygen mixed
together
Water
a pure
compound
formed from
hydrogen
burning in
oxygen
Tin (Stannum)
Sn
Solid
Zinc
Zn
Solid
The complete list of the elements with their corresponding symbols
is shown in the Periodic Table on p. 294.
H
The gaseous elements helium, neon, argon,
krypton, xenon and radon are composed of separate
and individual atoms. When an element exists
as separate atoms, then the molecules are said
to be
monatomic
. In chemical shorthand these
monatomic molecules are written as He, Ne, Ar, Kr,
Xe and Rn respectively.
O
O
H
O
H
O
H
O
H
H
H
O
H
H
H
H
H
O
H
O
H
H
H
O
O
H
H
H
H
O
O
H
H
H
H
Figure 2.6
The element hydrogen reacts with the element oxygen to
produce the compound water.
