Elements, Compounds And Mixtures

KS3 Chemistry by Atif Choudri, BSc
Agenda
• Atoms
• Elements Introduction
• Elements Contd.
• Compounds
• Mixtures
• Exercises

Atoms
• Atoms are the basic building blocks of matter everything is made of
atoms
• They cannot be seen individually as they are extremely small. About
10,000 times smaller than bacteria!
• We model atoms sometimes like little balls. In reality, they have a
structure
Most of the mass of a proton is located in the “Nucleus” which consists
of protons and neutrons.
Electrons orbit the nucleus like planets orbit the sun in orbits known as
“shells”

Elements Introduction
• 90 or more different types of atom actually occur naturally here on
Earth. Elements can be found in the Periodic Table. Every atom has it’s
own unique symbol some are given as below. It would be good to
remember some of the common and not so common ones:

Elements Definition
Definition: An element is a substance that consists of only one type of
atom. For instance, in the element Silicon all the atoms are Silicon
atoms. Elements cannot be broken down into simpler substances in the
lab.

Elements Table and Structure

What is a compound?
Definition: A compound is a substance that consists of 2 or more
different types of atoms of an element chemically bonded together

What is a Mixture
• A mixture is when two or more substances that are mixed together
but not chemically combined.

Test your Knowledge
• Which of these is an element, a compound or a mixture.