1 ELEMENTS The Simplest Matter. 2 Elements Definition of Elements: An element is a substance which...

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ELEMENTS The Simplest

Matter

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ElementsDefinition of Elements:

An element is a substance which cannot be split into two or more simpler substances by chemical reactions.

For e.g. Sodium(Na), Magnesium(Mg), Carbon(C)

Oxygen gas (O2), etc

Every element is given a name and a chemical symbol.

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Abundance of Elements

• 109 have been discovered so far

• 92 elements occur naturally while the rest are man-made

• Most elements are found combined with other elements in the form of ores or minerals

• Some elements such as gold, sulphur, oxygen, nitrogen, neon, helium occur naturally in their free or uncombined state

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For your interest …

Find out the following:

(a)  What is the most abundant element in the       earth's crust?

(b)  What is the most abundant metal in the       earth's crust

(c)  What is the most abundant element in the       earth's atmosphere?

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Classification of Elements –

Periodic Table • The elements have been classified according to their chemical properties into a chart called the Periodic Table as shown below.

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In the periodic table…In the periodic table,

• Each vertical column is called a group.

Elements in a group have similar chemical properties. Each group has its own unique properties.

• Each horizontal row is called a period.

Elements in a period from left to right show a gradual change from metallic properties to non-metallic properties.

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In the periodic table…In the periodic table,

• Each element is represented by chemical symbol.

Chemical Name Chemical Symbol

Aluminium Al

Zinc Zn

Copper Cu

Magnesium Mg

Mercury Hg

Note: Shown on this slide are common elements you need to know.

In the periodic table…Chemical Name Chemical Symbol

Iron Fe

Carbon C

Sulfur S

Chlorine Cl

Nitrogen N

Iodine I

Hydrogen H

Oxygen O

Note the spelling of “sulfur”. No longer “sulphur”.By extension,Sulfate, sulfide,Sulfuric acid.

Note: Shown on this slide are common elements you need to know.

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Classification of Elements

Elements can be classified into :

• Metals

e.g. aluminium, calcium, copper, mercury, iron, zinc

• Non-metals

e.g. oxygen, hydrogen, helium, iodine, sulphur

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Physical Properties of Metallic & Non-metallic

ElementsMetallic element Non-metallic

elements

High melting and boiling points (exists as solids at room temperature except for mercury which exists as a liquid)

Low melting and boiling points (exists as solids, liquids or gases at room temperature)

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Physical Properties of Metallic & Non-metallic

ElementsMetallic element Non-metallic

elements

Good heat conductors

Poor heat conductors

Good electrical conductors

Poor electrical conductors (except for graphite)

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Physical Properties of Metallic & Non-metallic

ElementsMetallic element Non-metallic

elements

Ductile (can be drawn into wires)

Non-ductile or snap easily (cannot be drawn into wires)

Malleable(can be beaten into shapes without breaking)

Brittle (easily broken when beaten)

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Physical Properties of Metallic & Non-metallic

ElementsMetallic element Non-metallic

elements

Shiny (lustrous)

Dull in appearance (not lustrous)

High densities Low densities

Sonorous(produce a ringing sound when hit)

Not sonorous

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Uses of some elements

Sulfur

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Uses of some non-non-metallicmetallic elements

Carbon exists in several different forms (called allotropes) -diamond, graphite, soot, charcoal

Diamond is the hardest natural substance.

Thousands of tiny diamonds are attached to saws and drills for cutting concrete and drilling into rocks.

Uses: pencil leads, fuel, constitutes living tissues

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Uses of some non-non-metallicmetallic elements

Uses: fertilisers, freezing agent for food, constitutes plants and animal proteins

This gas is an unreactive element. It does not combine readily with other elements.Hence it can be used in the packing of food

It is also used in the making of fertilisers.

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Uses of some non-non-metallicmetallic elements

Uses: drugs, fireworks, to harden rubber, insecticides,

medicinal drugs

Sulfur is a yellow non-metallic element, found in the free state.

It is used to harden rubber used for making tyres.

It is also used in the manufacture of sulfuric acid, pesticides and drugs.

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Uses of some non-non-metallicmetallic elements

Uses: antiseptic

Iodine is a non-metallic element that sublimes when heated to form a violet vapour.

When dissolved in ethanol, it forms tincture of iodine, used as an antiseptic.

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Uses of some non-non-metallicmetallic elements

Uses: combustion, respiration

Oxygen is the most important gaseous element to all living organisms on earth

They need it for respiration.

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Uses of some non-non-metallicmetallic elements

Name of non-metallic element

Uses

Chlorine Bleaching powder, kills bacteria, used in making plastics (PVC)

Fluorine Prevents tooth decay

Silicon Transistors, manufacture of steel

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Uses of some metallicmetallic elements

Uses: roofs, dry cell casings

Zinc is used to coat iron sheets to make galvanised iron.

It is also mixed with copper to form the alloy, brass.

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Uses of some metallicmetallic elements

Uses: fluorescent lamps, thermometers

Mercury is the only metallic element that is a liquid at room temperature.

It is used in liquid-in-glass thermometers, fluorescent lamps and some dental fillings

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Uses of some metallicmetallic elements

Uses: fireworks

Magnesium burns with a white dazzling light and so it is used in distress flares.

It is also used in making fireworks.

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Uses of some metallicmetallic elements

Uses: pots and pans, foil wraps, window and door frames, light alloy

Aluminium, being strong, and of low density is used to make aeroplane parts.

This metal is also used to make drink cans, cooking utensils and ladders.

Being a good electrical conductor and of low density, it is also used to make overhead electricity cables.

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Uses of some metallicmetallic elements

Uses: electrical wires and switches, coins, water pipes, tanks

This metal is commonly used to make electrical wires as it is a good electrical conductor and is inexpensive.

It is also used to make water pipes.

When mixed with tin, it forms the alloy called bronze and when mixed with zinc, it forms the alloy called brass.

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Uses of some metallicmetallic elements

Name of metallic element Uses

Calcium For the body to grow strong teeth and bones

Iron Manufacture of steel, railings, grills, cooking utensils

Lead Lead shots, accumulators