Atoms are the basic units of matter and are made up of protons, neutrons, and electrons. Elements are pure substances made of only one type of atom and are represented by chemical symbols. Compounds are formed when different types of atoms combine via atomic bonds to form molecules consisting of two or more elements represented by chemical formulas using subscripts.

1. Basic Chemistry Concepts
• Atoms and elements
– Element: a basic unit of matter that can’t be
further simplified, such as oxygen or iron. each
element is assigned a symbol of one or more
letters, such as ofor oxygen and Fe for iron.
– Atom: the smallest part of an element that
cannot be broken down by chemical means.
Each atom is in turn made up of protons (+),
neutrons (0), and electrons (-)
– Atoms have no net charge, so there are an
equal number of protons and electrons, which
is the atomic number.

2. Basic Chemistry Concepts
• Compounds, molecules, and atomic
bonds
– Atoms combine to form molecules.
– A collection of like molecules that consist
of two or more different kinds of elements
is called a compound. molecules are
represented by using the symbols of the
elements with subscripts to tell how many
there are of each. (H2O)
– Atoms join together by either sharing or
donating and accepting of electron
forming atomic bonds