How Ionic Compounds Are Named
When you name ionic compounds, you write the name of the metal first and then the nonmetal. Suppose that you want to name the compound that results from the reaction of lithium and sulfur. You first write the name of the metal, lithium, and then write the name of the nonmetal, adding an -ide ending so that sulfur becomes sulfide.
Ionic compounds involving polyatomic ions follow the same basic rule: Write the name of the metal first, and then simply add the name of the nonmetal (with the polyatomic anions, it is not necessary to add the -ide ending).
When the metal involved is a transition metal with more than one oxidation state, there can be more than one way to correctly name the compound.
For example, suppose that you want to name the compound formed between the cation:
and the cyanide ion:
The preferred method is to use the metal name followed in parentheses by the ionic charge written as a Roman numeral: Iron(III).
But an older naming method, which is still in use, is to use -ous and -ic endings. The ion with the lower oxidation state (lower numerical charge, ignoring the + or -) is given an -ous ending, and the ion with the higher oxidation state (higher numerical charge) is given an -ic ending.
So the compound can be named:
Sometimes figuring out the charge on an ion can be a little challenging (and fun), so suppose you want to name the following ionic compound:
The sulfate ion has a 2- charge, and from the formula you can see that there are two of them. Therefore, you have a total of four negative charges. The ammonium ion has a 1+ charge, so you can figure out the charge on the iron cation.
Because you have a 4- for the sulfates and a 1+ for the ammonium, the iron must be a 3+ to make the compound neutral. So the iron is in the Iron(III), or ferric, oxidation state. You can name the compound:
And, finally, if you have the name, you can derive the formula and the charge on the ions. For example, suppose that you’re given the name cuprous oxide. You know that the cuprous ion is:
The oxide ion is:
Applying the crisscross rule, you get the following formula:
Chemistry Glossary
Archimedes Principle
A principle discovered by the Greek mathematician Archimedes which states that the volume of a solid is equal to the volume of water it displaces.
Chemistry Glossary
atomic number
The number of protons in the nucleus of an atom.
Chemistry Glossary
Bohr model
A model of atomic structure developed by Niels Bohr, a Danish scientist. In this model, electrons occur in orbits of differing energy levels around the nucleus of an atom.
Chemistry Glossary
condensation
The change in the physical state of matter from a gaseous state to a liquid state.
Chemistry Glossary
deposition
The change in the physical state of matter from a gaseous state to a solid state without ever becoming a liquid. The reverse of sublimation.
Chemistry Glossary
electrolytes
Substances that can conduct electricity either in the molten state or when dissolved in water.
Chemistry Glossary
electron configuration notation
A method used by chemists to represent electrons in bonding and chemical reactions.
Chemistry Glossary
electronegativity
A measure of an atom’s strength to attract a bonding pair of electrons to itself.
Chemistry Glossary
energy level diagram
A method used by chemists to diagram the electrons for an atom (including orbitals and subshells) in bonding and chemical reactions.
Chemistry Glossary
heterogeneous mixture
A mixture whose composition varies from position to position within a sample.
Chemistry Glossary
homogeneous mixture
A mixture whose composition is the same from position to position within a sample.
Chemistry Glossary
isotopes
Atoms of the same element that have varying numbers of neutrons.
Chemistry Glossary
mass number
The sum of the protons and neutrons in a particular isotope; also called atomic weight.
Chemistry Glossary
nonelectrolytes
Substances that do not conduct electricity in the molten state or when dissolved in water.
Chemistry Glossary
nuclear fission
A nuclear reaction in which an atom’s nucleus splits into smaller parts.
Chemistry Glossary
nuclear fusion
A process in which lighter nuclei of atoms join together into a heavier nucleus; essentially the opposite of nuclear fission.
Chemistry Glossary
nuclear reaction
Any reaction that involves a change in nuclear structure.
Chemistry Glossary
periodic table
A table that displays all known chemical elements in an arrangement that is based on the properties of the elements; changes over time as new elements are discovered.
Chemistry Glossary
quantum mechanical model
A model of atomic structure that is based on mathematics and can be used to explain observations made on complex atoms.
Chemistry Glossary
radioactivity
The spontaneous decay of an unstable nucleus in an atom.
Chemistry Glossary
SI system
A worldwide measurement system that is based on the older metric system. The SI comes from the French Systeme International.
Chemistry Glossary
sublimation
The change in the physical state of matter from a solid state to a gaseous state without ever becoming a liquid (such as dry ice).
Chemistry Glossary
valence electrons
The electrons in the outermost energy level of an atom, the farthest away from the nucleus.
