Element and Compound

Building Blocks (Year 8)

Syaiful Zubir, August 2010


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Particle and Kinetic Theory

Substances are made up of particles. The state of the substance depends on the arrangement of the particles.

Solid

Particles held tightly Very close together Regular arrangement Vibrate Can’t move from place to place

Liquid

Particles held weakly Very close together Random arrangement Vibrate Constantly move past each other

Gas

No attraction between particles Far apart Random arrangement Vibrate Move quickly in all directions

The Three States of Matter

Click to move onSyaiful Zubir, August 2010


Atoms and Elements

Elements consist of only one type of particle. We call these particles atoms.They cannot be split into simpler, smaller particles by chemical methods.

There are about 109 elements known at the moment (2004). Don’t worry, you don’t have to learn them all!

The elements each have a name and a symbol.

By the end of year 9, you must know the first twenty elements off by heart, so it is a good idea to start learning them now!



The First Twenty Elements

AtomicNumber

Symbol

NameAtomicNumber

Symbol

Name

1 H hydrogen 11 Na sodium

2 He helium 12 Mg magnesium

3 Li lithium 13 Al aluminium

4 Be beryllium 14 Si silicon

5 B boron 15 P phosphorus

6 C carbon 16 S sulphur

7 N nitrogen 17 Cl chlorine

8 O oxygen 18 Ar argon

9 F fluorine 19 K potassium

10 Ne neon 20 Ca calcium



Arranging the Elements

As you know, the elements are arranged in the Periodic Table.

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The elements were first arranged in this way by Dmitri Mendeleev, a professor at St. Petersburg University, in 1869. His arrangement was based on atomic mass.

When Mendeleev was setting out the table, only 63 elements had been discovered. His big idea was to leave gaps for yet to be discovered elements. He was able to predict the properties of some of these elements, including silicon and boron. When his predictions were shown to be accurate his table became accepted, and it is the basis of the one we use today.

‘Maybe one day we’ll understand why Dmitri always lays out his blocks this way!’

Syaiful Zubir, August 2010


Arranging the Elements : Metals and Non-Metals

Most of the elements are metals. The non-metals are found to the top right of the periodic table.The metals and non-metals are separated by a sort of ‘stair case’.



Arranging the Elements : Groups and Periods

The columns of the periodic table are called Groups. Elements in a group have similar properties.

Group1

Group2

Group3

Group4

Group5

Group6

Group7

Group0

Group 1 : Alkali metalsGroup 2 : Alkaline earth metals Group 7 : HalogensGroup 0 : Noble gases

Transition metals

The horizontal rows are called Periods.



Properties of Metals

Metals have the following properties :

They conduct electrical energy well

They conduct thermal energy well

They are shiny

They are malleable (can be hammered into shape)

They are ductile (can be drawn out into wires)

They are sonorous (make a ringing sound when hit)

All except mercury are solids at room temperature

Only a few metals are magnetic.

Magnetism is not a property of most metals!



Properties of Non-Metals

Non-metals have the following properties :

They are poor conductors of electrical energy

They are poor conductors of thermal energy

Many of them are gases

They are brittle if they are solid

Both a diamond and a pencil ‘lead’ are made of the same element – carbon.



Elements, Molecules and Compounds

Some elements, such as the noble gases, exist as individual atoms.

Often, elements consist of two or more atoms joined together. We call these molecules.

If more than one type of atom is in a molecule, we call it a compound.



Mixtures

This is a mixture of elements made up of atoms, elements made up of molecules, and compounds.

In a mixture, the particles are not joined together.

Atom, molecule or compound?(click for answer)



atom

molecule

compound



magnesium + oxygen (click for answer)magnesium + oxygen magnesium oxide

Naming Compounds

If we heat copper in air, it reacts with the oxygen to make a new compound. We call this compound copper oxide.

We can write a word equation for this :

copper + oxygen copper oxide

Most metals will react with oxygen to form an oxide. For example :

When metals react with oxygen we often say they are corroding.

Iron is a very common metal (steel is mostly made of iron), and it reacts with oxygen to make the compound iron oxide. This is such a common reaction that we give the compound iron oxide a common name – rust!

Iron is the only metal that rusts. The correct term to use for other metals is that they corrode.



More Oxygen Compounds

Oxygen also reacts with some non-metals to form compounds.

When carbon burns, the following reaction happens :

carbon + oxygen carbon dioxide

C + O2 CO2

And of course, oxygen reacts with hydrogen to form a very common compound!

hydrogen + oxygen water

2H2 + O2 2H2O

A molecule of carbon dioxide – one atom of carbon and two atoms of oxygen

A molecule of water – one atom of oxygen and two atoms of hydrogen



magnesium + sulphur (click for answer)magnesium + sulphur magnesium sulphide

More Compounds

Naming compounds is quite straightforward when you get used to it. When metals react with chlorine, they form chlorides.

sodium + chlorine sodium chloride

lithium + chlorine (click for answer)lithium + chlorine lithium chloride

With sulphur, sulphides are formed.

iron + sulphur iron sulphide

Salt (sodium chloride) crystals are made up of millions of sodium and chlorine atoms.



Element or Compound?

methane, CH4

(Click for answer)

compound

sulphur, S8

(Click for answer)

element

hydrogen peroxide, H2O2

(Click for answer)

compound

sulphuric acid, H2SO4

(Click for answer)

compound

oxygen (ozone), O3

(Click for answer)

element

carbon (buckyball), C60

(Click for answer)

element



Testing for Gases

In some chemical reactions, gases are given off. There are several simple tests we can do to find out which element or compound a gas is. Here are two of them.

Carbon dioxide

•Bubble the gas through lime water.•If the lime water turns milky, the gas is CO2.

Oxygen

•Hold a glowing splint in the gas.•If the splint relights, the gas is O2.



You have now reached the end of the revision presentation for the ‘Building Blocks’ topic.

I hope you have found it useful. If you have any ideas to improve this presentation please let Mr. Syaiful Zubir know.

Thank you for looking at this work, and good luck in your test.

Click to finishSyaiful Zubir, August 2010

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Element and Compound