<P> In general, organic acids follow the normal rules with C and H coming first in the formula . For example, the formula for trifluoroacetic acid is usually written as C HF O. More descriptive formulas can convey structural information, such as writing the formula for trifluoroacetic acid as CF CO H. On the other hand, the chemical formulas for most inorganic acids and bases are exceptions to the normal rules . They are written according to the rules for ionic compounds (positive first, negative second), but they also follow rules that emphasize their Arrhenius definitions . To be specific, the formula for most inorganic acids begins with hydrogen and the formula for most bases ends with the hydroxide ion (OH). Formulas for inorganic compounds do not often convey structural information, as illustrated by the common use of the formula H SO for a molecule (sulfuric acid) that contains no H-S bonds . A more descriptive presentation would be O S (OH), but it is almost never written this way . </P> <P> Compounds may have several possible phases . All compounds can exist as solids, at least at low enough temperatures . Molecular compounds may also exist as liquids, gases, and, in some cases, even plasmas . All compounds decompose upon applying heat . The temperature at which such fragmentation occurs is often called the decomposition temperature . Decomposition temperatures are not sharp and depend on pressure, temperature, and the concentration of each species in the compound . </P> <P> Compounds are held together through a variety of different types of bonding and forces . The differences in the types of bonds in compounds differ based on the types of elements present in the compound . </P> <P> London dispersion forces are the weakest force of all intermolecular forces . They are temporary attractive forces that form when the electrons in two adjacent atoms are positioned so that they create a temporary dipole . Additionally, London dispersion forces are responsible for condensing non polar substances to liquids, and to further freeze to a solid state dependent on how low the temperature of the environment is . </P>

Two major types of chemical reactions in which molecules are formed or broken are called