Final answer:
In chemistry, prefixes are added to binary molecular compounds to indicate the number of atoms of each element, and to SI units to simplify the expression of measurements by signifying multiples or fractions of ten.
Step-by-step explanation:
In chemistry, prefixes are added to the names of binary molecular compounds to indicate the number of atoms of each element present in the compound. For instance, when naming carbon dioxide, the prefix di- indicates that there are two oxygen atoms. It is important to know when to use these prefixes to provide clear and specific names for chemical compounds.
The following rules describe when to add prefixes:
- If there is more than one atom of the first element in a compound, an appropriate prefix indicating the number of atoms is used before its name.
- The name of the second element is always prefixed and its name is altered to end in -ide.
- To avoid awkward pronunciation, when a prefix ends in a vowel and is followed by an element name that begins with a vowel, the ending vowel of the prefix is often dropped (e.g., tetroxide instead of tetraoxide).
- For non-metals, these prefixes are used to specify quantity. For metals, Roman numerals indicate the charge of the ion.
In binary molecular compounds consisting solely of nonmetals, prefixes such as 'mono-', 'di-', 'tri-', etc., are used to designate the number of atoms. For example, CO is carbon monoxide and CO₂ is carbon dioxide, where 'mono-' signifies one oxygen atom and 'di-' signifies two.
Metric prefixes are another area in chemistry where prefixes based on Latin or Greek terms are used to express the multiple or fraction of units, helping make these units more manageable. These prefixes are connected to the International System of Units (SI) which is based on multiples of ten.