Basic Chemistry Review
Structure of Matter
Atom: smallest unit of matter
Net charge of:
Proton Positive (+)
Neutron Neutral (o)
Electron Negative (-)
A is the mass number which is the total number of protons and
neutrons. X is the symbol for the element. Z is the atomic
number- the number of protons and electrons in each atom of
Isotopes: the same atomic number but different atomic masses
due to different numbers of neutrons
Radioisotope: An isotope of a chemical element that has an unstable nucleus and emits radiation during
its decay to a stable form, have important uses in medical diagnosis, treatment, and research
Half-life: The length of time it takes for a substance undergoing decay to decrease by half
Electron shells and Orbitals
The volume of space around the nucleus where electrons are most likely found is called the orbital.
Those electrons available for bonding are called valence electrons. The number and arrangement of its
valence electrons in these “s” and “p” orbitals determine the behaviour of the atom.
Ionic bond: complete transfer of electron(s) Covalent bond: electron(s) shared in orbital space
Atoms react to achieve stability, which usually results in the release of energy (to a lower energy state).
Atoms combine to complete their outer shell and become stable; they form bonds- a force holding two
atoms together. A compound molecule results from the chemical bonding of two or more different
atoms. During bonding, an energy exchange occurs and atoms assume a more stable configuration. A
molecule will tend to move until it is next to a molecule with which it can form the strongest possible
bond and achieve stability.
Strong bonds are not easily broken whereas weak bonds exist only for a second or two. Strong bonds
are short, the atoms are close together; weak bonds are longer, the atoms are further apart.
Energy must be added to break a bond, and energy is released when a bond is formed. The energy
required to break a bond is the same as the energy released when the bond is formed. Biochemistry
Types of chemical bonds
Intramolecular bonds: bonds within a molecule that hold the atoms of a molecule together
Intermolecular bonds: bonds between molecules
Electronegativity: a chemical property that describes the tendency of an atom or a functional group to
attract electrons (or electron density) towards itself
Covalent bond- This type of bond is a pure sharing of electrons within the bond. The difference in
electronegativities is essentially zero. O 2s an example of a pure covalent b