Learning goals

At the end of this section, you should be able to:

1. ​Write the definition of element

   ​

2. ​State the chemical symbol of elements using Periodic Table

Subject | Subject

Some text here about the topic of discussion

It is a pure substance that cannot be broken down into two or more simpler substances by chemical processes.

​

​Some text here about the topic of discussion.

Element​

Sugar is not an element.

When heated, it breaks down into carbon and water vapour.

​

​Some text here about the topic of discussion.

Is Sugar an element?

​

Two key questions to check whether a substance is an element.

1. Can the substance be broken down into two or more simpler substances?

   ​

2. Can it be found in the periodic table? ​

Subject | Subject

Some text here about the topic of discussion

• Chemists use chemical symbols to represent elements. 

  ​

• Each symbol is unique, consisting of one or two letters.

​

​Some text here about the topic of discussion.

Chemical symbols of elements

​

Elements can be classified into:

1. Metals

2. Metalloids

3. Non-metals​

​Some text here about the topic of discussion.

​Classifying elements

Elements are classified based on:

1. Metallic and non-metallic properties

2. Physical states (at r.t.p)​

​Some text here about the topic of discussion.

​Classifying elements

​Some text here about the topic of discussion.

​Classifying elements

Elements exist in atoms and molecules.

​

​Some text here about the topic of discussion.

Atoms and Molecules

​

• Atoms are the smallest particles of an element that have the chemical properties of that element.

• The atoms of an element are different from that of another element.

​Some text here about the topic of discussion.

Atoms and Molecules

​

• A molecule is a group of two or more atoms that are chemically combined (joined together).

• Molecules exist in diatomic or polyatomic.​

​Some text here about the topic of discussion.

Atoms and Molecules

​

What is a compound?

​

​A compound is a pure substance that contains two or more elements that are chemically combined in a fixed ratio.

​

​Some text here about the topic of discussion.

Compound​

Ions

Molecules

What are compounds made of?

Some text here about the topic of discussion

A compound has different properties from the elements that form it.

​

​Some text here about the topic of discussion.

Properties of Compounds

Names of Compounds

Each compound has a chemical name indicating the elements it contains.

Subject | Subject

Some text here about the topic of discussion

Chemical Formulas of Compounds

A compound can be represented by a chemical formula.

The chemical formula shows:

• the types of elements present;

• the ratio of the different atoms present.​

Subject | Subject

Some text here about the topic of discussion

Composition of Compounds

Every compound has fixed compositions of the different elements it contains.

Chemical formula can be deduced by the ratio of atoms present in a compound.​

Subject | Subject

Some text here about the topic of discussion

Decomposition of Compounds

• A chemical reaction is necessary to separate the elements in a compound.

• In thermal decomposition, heat is used to break down compounds into elements or simpler compounds.

• Compounds can also be broken down by using electricity. This process is known as electrolysis. 

Subject | Subject

Some text here about the topic of discussion

Learning goals

At the end of this section, you should be able to:

1. define a mixture;

2. differentiate between compounds and mixtures.

Some text here about the topic of discussion

Mixtures are made up of two or more substances that are not chemically combined.

​Some text here about the topic of discussion.

What are mixtures?

There are a few scenarios on how substances are mixed together physically:

1. mixture of elements

2. mixture of compounds

3. mixture of compound and element ​

​

Type of mixtures