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• Every substance is
either an element or
a compound.
• Elements are the
simplest form of
matter.
• Elements are the
building blocks for
all other substances.
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ELEMENTS
• Simple pure substances
• all atoms the same
• can’t be divided/broken/decomposed by
physical or chemical means
• some in free state but most combined with
other elements
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substances
Pure
substances
mixtures
elements
compound
s
hetero homo
meta
l
nonmet
al
ionic
molecul
ar
alloys
solutio
ns
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Symbols
• All elements have
their own unique
symbol.
• It can consist of a
single capital letter,
or a capital letter
and one or two
lower case letters.
C Carbon
Cu
Copper
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Classification of elements
1. Classification by state
elements are classified by their physical
state at room temp.
of the 92 naturally elements, 11 are
gases, 2 are liquids (Hg, Br2), 79 are solid
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Classification of elements
2. Classification of elements as metals, non-
metals, and metalloids
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Properties Metals
a. Usually solids except Mercury
(liquid at room temp). Their MP and
BP are usually high
b. Usually hard and dense
c. Good conductor of heat and
electricity
d. Malleable and ductile
e. Shiny, grey in color (except gold
and copper). They can be polished.
f. sonorous
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Properties of Non-Metals
a. Usually solids & gasses except
Bromine (liquid at room temp)
b. Non-metals are poor conductors
of heat and electricity.
c. Non-metals are not ductile or
malleable.
d. Solid non-metals are brittle and
break easily.
e. Low melting/boiling point
f. Most of non-metals softer than
metal, they have low density
Sulfur
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Properties of Metalloids
a. Metalloids (metal-like)
have properties of both
metals and non-metals.
b. They are solids that can
be shiny or dull.
c. They conduct heat and
electricity better than non-
metals but not as well as
metals.
d. They are ductile and
malleable.
Silicon
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Classification of elements
• 3. Classification of elements as in the
Periodic Table
elements are classified by their physical
state at room temp.
of the 92 naturally elements, 11 are
gases, 2 are liquids (Hg, Br2), 79 are solid
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Electron arrangement
• The electron arrangements of atoms are
linked to position in the periodic table.
• Elements in the same group have the same
number of electrons in their outer shell.
• For the main group elements, the number of the
group is the number of electrons in the outer
shell.
• The periods also have numbers. This number
shows us how many shells of electrons the atom
has.
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What are Elements Made of?
• An element consist of a particular type of
atom
• Atoms of one element are different from
the atopms of any other element.
• In some elements, atoms are joined with
other atoms in small groups (molecules) :
Cl2, Br2, O2, H2, I2, P4, S8
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Group 1- Alkali Metals
• Most reactive metals that occur
• React vigorously with water produce
H2 and alkalin solution
• Melting point become lower
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Group VII-the Halogen
• Most reactive non-metal
• Reactivity decreases down the
group
• All poisonous and have a similar
strong smell
• Form diatomic molecules
• With hydrogen 🡪 strong acid when
dissolve in water
• A series compounds with other
elements 🡪 halides
• React with metal 🡪 metal halide
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The chemical reactivity
of the halogen
• 2Al + 3Cl2 🡪 2AlCl3 (metal glow
white and forms aluminum
cloride)
• H2 + Cl2 🡪 2HCl (explosive)
• Cl2 + H2O 🡪 HCl + HClO
(Chlorine water 🡪 oxidising
agent)
• Some reaction in halogen (Table
3.2)
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Group VIII- the Noble
Gases
• Unreactive
• Helium is used in airships and
baloon
• Argon is used to fill light bulbs
• Neon : brightly coloured
• Melting and boiling point are low
• Very stable
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The transition Element
• Less reactive than the metals in
group I and II
• Hard and strong
• High density
• High melting and boiling point
• Many of compounds are
coloured
• More than 1 valency
