Do anions always have the same negative charge? Do they have fractional charges?

Answer 1

1 An anion (pronounced ann-ion) is an atom or molecule that has a negative charge. Cations are abundant in seawater and hard water. The Halogens are missing one electron in their last shell, so they very quickly absorb one electron and have a charge of -1. Most of the common anions are not single atoms, however, but groups of atoms, called molecules. Example include sulfates and carbonates.

Note that there is a naming convention. The "-ide" ending refers to a simple anion. The anion of chlorine is chloride. The anion for fluorine is fluoride. Sulfur becomes sulfide. Anions that contain oxygen often end in "-ate". Carbonate, sulfate and phosphate are examples. This will help you remember which is which.

It is worth memorizing the more common anions because they are so common and have such a great impact upon our lives. The cations that are most common react with the anions that are most common, especially when the water they are in dries up. The products of these reactions are called "salts". The name for the compound is the name of the cation followed by the name of the anion, for example, sodium chloride. 1

The total charge of the salt should equal zero. For example:

Three sodium cations (Na+) are needed to make a neutral salt with one phosphate anion (PO4-3) and the formula for the salt is then Na3PO4

Ions from water molecules - a special case. Water, H2O, can be thought of like this:

H-O-H or H+ and OH-

Sometimes water has more H+ ions than OH- ions. This water is said to be "acidic". In fact, acidity on the pH scale is a measurement of the number of H+ in water.

On the other hand, water can have more OH- ions, or "hydroxides ions". The water is then said to be basic, alkaline, or caustic. The pH scale, above 7, measures the number of hydroxide ions.

Both hydrogen and hydroxide ions are very reactive. That is why acids and bases burn you!

so thats the meaning

Answer 2

An anion composed of a single atom should always have the same charge- the charge depending on the particular anion. Complex anions such as NO3^- will ALMOST always have the same charge.
There are complications however. Iodine for example, can form, the iodide anion: I^-, in which the charge is -1 for the iodine. However, it can also sometimes form the tri-iodide anion I3^-, which is actually an equilbrium between I2 and I^-. Nonetheless, the charge per iodine atom in the triiodide anion is formally, -1/3.

NO2 is another complicated example. Because nitrogen is capable of forming more than one stable oxidation state, NO2 can exist as a neutral molecule, as the nitronium cation: NO2^+, or as the nitrite anion NO2^-.

Answer 3

Anions have negative charges. The actual charge on the anion depends on the type of anion.

No, an anion cannot have a fractional charge if it is completely dissociated from the counter-cation. Atleast, not until someone discovers how to split an electron.

Answer 4

Yes anions and cations have always the same negative charge. You can not change.

But there are molecules as water which have polar bouds; In water, it seems that oxygen is more negative than hydrogen, giving an "hypothetical" fractional charge without real physical meaning