Structure of Atoms

An atom is composed of three types of subatomic particles: protons, neutrons and electrons.
Protons and neutrons are located in the nucleus (the centre) of an atom. Protons possess a positive charge, whereas neutrons are neutral with no charge.
Electrons are found in energy levels (shells) around the nucleus and carry a negative charge.
The types and numbers of these particles determine the chemical properties of the atom.
Naming an atom is usually done by the number of protons in its nucleus - this number is what we refer to as the atomic number.
The total number of protons and neutrons together is known as the mass number.
Atoms are most stable when their outermost shell is full; this desire to fill the electron shells is a major driver of chemical reactions.
Isotopes are variations of an atom with the same number of protons, but differing numbers of neutrons.
Types of bonds include covalent bonds (sharing of electrons between two or more atoms) and ionic bonds (transfer of electrons from one atom to another).
The reactivity of an atom is highly influenced by the number of electrons in its outermost shell. Atoms will gain, lose or share electrons to achieve a full outer shell.
Understand the concept of ions, which are atoms or sets of atoms with a positive or negative charge due to the loss or gain of electrons respectively.
Some important elements in health and life sciences include Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, and Sulfur. Understand the atomic structure of these elements as well as their role in biological molecules.