Atoms and Molecules - Grade 6

Atoms and Molecules- Chemistry

1. ATOMS AND MOLECULES CHEMISTRY MADE BY SALAR ALI

2. What is an atom? An atom is defined as the smallest particle of an element that can exist. Atoms are the building blocks of all matter. All matter, living or non-living, is made up of atoms. Atoms are so small that we cannot see them without the help of electron microscopes. Each element is made up of its own type of atom. The atoms of different elements are different in sizes.

3. Representing atoms Circles are commonly used to represent atoms. Another way of representing different kinds of atoms is by using spheres of various sizes and colours . Representation of atoms using models and diagrams makes the study and understanding of atoms and molecules. Na

4. What is a molecule? A molecule is made up of two or more atoms of the same kind or of different kinds chemically combined together. Molecules exist in both elements and compounds. Molecules in elements consist of a fixed number of one kind of atom only. In some cases, three identical atoms may combine to form a molecule, as in the ozone molecule which is made up of three oxygen atoms. Molecules in compounds consist of a fixed number of two or more different kinds of atoms chemically combined together.

5. Chemical Formula The atomic composition of a water molecule can be described either In words, i.e. ‘Each molecule of water contains two atoms of hydrogen and one atom of oxygen chemically combined together.’ or by its chemical formula, i.e. H₂O The chemical formula of a molecule shows the number and kinds of atoms contained in it. The chemical formula of a molecule of an element is denoted by the chemical symbol of the element and a subscript showing the number of atoms in the molecule. For example, H₂ denotes a molecule of hydrogen which consists of two hydrogen atoms. Let us take a look at some examples on the next slide.

6. EXAMPLES CHEMICAL FORMULA MEANING CO Every carbon monoxide molecule contains one carbon atom and one oxygen atom chemically combined together. H₂O Every water molecule contains two hydrogen atoms and one oxygen atom chemically combined together, C₁₂H₂₂O₁₁ Every sucrose molecule contains 12 carbon atoms, 22 hydrogen atoms and 11 oxygen atoms chemically combined together.