Atoms bond in two general ways, either by sharing electrons between atoms or through transferring one or more electrons from one atom to another atom. When the electrons in molecules are transferred, thus forming an electrically neutral particle, an ionic bond between them is formed. This means that one element gives away a certain number of electron to another element that receives them. Ions are electrically charged particles formed after electrons are transferred between atoms. Ionic bonds are the strongest types of bonds and occur between metals and non-metals. Molecular compounds occur when two nonmetallic elements combine; between them, a covalent bond is formed. This means that the electrons are shared between two atoms equally. The smallest molecules only have two atoms and are referred to as diatomic molecules. Molecular formulas are drawn to show the composition of molecules. Molecules do not conduct electricity. Organic chemistry is the study of compounds with carbon. Hydrocarbons are compounds of hydrogen, carbon, and oxygen, such as methane, ethane, and propane. These compounds are the principal makeup of petroleum. Alcohols are another type of compound formed from hydrocarbons. When a compound is formed between a nonmetal and hydrogen the result is a hydride.

As said, chemical bonds hold the molecules together. The net force of attraction produced by the sharing of electrons between atoms is known as a covalent bond. The bond length refers to the average distance between the nuclei held together by a covalent bond, and the bond energy is the amount of energy needed to separate the two atoms of a covalent bond. To keep track of the electrons being used in a covalent bond, Lewis symbols are often used. Atoms generally form covalent bonds to form an outer shell having eight electrons, to meet the noble gas configuration, in what is known as the octet rule. Halogens, which have seven valence electrons, only need one covalent bond to complete their outer shell. Elements with six valence electrons, such as Oxygen, need two covalent bonds. Nitrogen, which has five valence electrons, needs three covalent bonds. Carbon, with four valence electrons, has four covalent bonds. This information can all be found on the Periodic Table of Elements. However, the octet rule just explains the majority of covalent structures; there are always exceptions to the rule. When two or more molecules combine, new bonds are formed. These are either Dipole-Dipole bonds, Hydrogen bonds or London Forces. Dipole-Dipole bonds imply that two polar molecules, such as water, are held together by the slight opposite charges they have. Hydrogen bonds, which are the strongest of the intermolecular forces, occur when hydrogen of one molecule meets with oxygen, fluorine or nitrogen of another. This strength is due to the great differences in electronegativity. London forces occur when the electron cloud of an atom "shifts." This creates a slight negative charge at one and a slight positive charge in the other. The larger the atom, the greater the shifting that is possible.