Chemistry : Atoms, Molecules, Elements and compounds
What is an Atom ?
All substances are made up of matter and the fundamental unit of matter is the atom. The atom constitutes the smallest particle of an element. The atom is made of a central nucleus containing protons (positively-charged) and neutrons (with no charge). The electrons (negatively-charged with negligible mass) revolve around the nucleus in different imaginary paths called orbits or shells.
What is an Element ?
An element is a substance made up of atoms of one kind. There are about 82 naturally-occurring elements and about 31 artificially-made elements as listed in the Periodic Table
What is Atomic Number and Atomic Weight ?
The elements are arranged according to increasing atomic numbers (along with their atomic mass) in a table called the Periodic Table.
What is a Molecule ?
A molecule is formed when atoms of the same or different elements combine. A molecule is the smallest particle of a substance that can normally exist independently.
What is a Compound ?
A compound is formed when atoms or molecules of different elements combine. In a compound, elements are chemically combined in a fixed proportion.
Practice Exercise for Chemistry Module on Atom and Atomic Structure