The names of some simple cations are listed in Table II. This is why it is called mercury I ion. Monatomic anions are named by adding the suffix -ide to the stem of the name of the nonmetallic elements from which the anion is derived. For example, Cl — is called chloride and S 2- is called sulfide. Like a cation, the charge carried by an anion is related to the ground-state electron configuration of the element and thus is related to the position of the element in the periodic chart. All the halogen anions they are called halide ions carry a -1 charge because the halogen group is one group to the left of the noble gases in the periodic chart.
The oxide and sulfide ions carry a -2 charge because they are located two groups away from the noble gases in the periodic chart. Following this logic, one can predict that the nitride ion and the phosphide ion must carry a -3 charge. Some of the simple anions and their names are listed in Table III.
The hydride, peroxide, superoxide, and carbide ions shown in blue are exceptions to the above rule. Notice that there are a lot more polyatomic anions than cations. Most polyatomic anions consist of a nonmetallic element combined with different numbers of oxygen atoms these polyatomic anions are called oxoanions.
Even though it seems that there is no simple rule in naming these ions, in fact, here are some guidelines to follow:. It should be noted that the acetate and oxalate ions in purple are organic ions. They follow the naming system of organic compounds. They are included for reference here, as they are commonly used in Chem A, A, and Elements in the same group of the periodic chart have similar chemical properties; hence, they often form similar polyatomic ions.
Therefore, if we know the name and formula for a particular polyatomic ion, then by analogy, we can determine the name and formula of the similar polyatomic ion of another element in the same group. For example, if one knows that chlorate ion is ClO 3 — , then, an educated guess for the formula of bromate ion is BrO 3 — and for iodate ion is IO 3 —. It is important to know the names of polyatomic ions, and it is equally important to be familiar with their size and shape.
Compounds of high ionic character Two types of compounds fall into this category: those consisting of a metal combined with a nonmetal e. For the sake of naming compounds, both of these categories will be classified as ionic compounds in this tutorial.
To name an ionic compound, one should name the cation first, and then name the anion with the word 'ion' omitted. It is not necessary to indicate the number of cations and anions in the compound because it is understood that the total positive charges carried by the cations must equal the total negative charges carried by the anions.
A few examples are listed below:. Some ionic compounds incorporate water molecules in their structure. These compounds are called hydrates. To name the hydrates, the number of waters of hydration is indicated by a Greek prefix following the name of the compound.
Determining the molecular formula from the compound's name is not always straightforward. This is because the number of cations and anions in a molecule is not specified in the name of an ionic compound. The following examples show how finding the molecular formula can be achieved in a systematic matter:. Al 2 S 3 is the answer. However, the suffix —ate in the word 'phosphate' is the hint of an oxoanion, a polyatomic ion.
You know that this compound is classified as an ionic compound. VPO 4 is the answer. Again, this compound is classified as an ionic compound. Give the chemical formulas for the following ionic compounds:. Compounds of high covalent character Compounds consisting of only nonmetals and no polyatomic ions belong to this category e. They will be called covalent compounds in this tutorial. To name the covalent compounds, name the electropositive or less electronegative element first.
Then, name the more electronegative element as if the more electronegative element is a simple anion ending with — ide. How does one know which element is the electropositive element? In the chemical formulas of covalent compounds, usually the symbol of the electropositive element precedes the more electronegative element e. NH 3 is an exception of this generalization.
If one follows this rule, then, SO 2 would be called sulfur oxide, and CO would be called carbon oxide. Very often, two nonmetals can combine to form more than one compound. To distinguish these compounds from each other, Greek prefixes are used to designate the numbers of atoms of one or both elements in the molecule. For historical reasons, some hydrogen-containing covalent compounds have nonsystematic names such as:.
Give the chemical formulas for the following covalent compounds:. Inorganic acids The rules used to name inorganic acids are different from those rules used to name the ionic and covalent compounds. For example, HNO 3 is called nitric acid, not hydrogen nitrate nor hydrogen nitrogen trioxide. How can one recognize an acid by looking at its chemical formula? For example, Magnesium Mg is a group 2 element and has two valence electrons.
Then it is a monatomic cation. But Noble gases never have monatomic ions since their atoms are very stable with a completed electronic configuration. The bonding between two monatomic ions with opposite charges can form a diatomic molecule. Here, the cation and the anion are attracted to each other via electrostatic forces.
For example, sodium chloride NaCl is made of sodium monoatomic cation and chloride monatomic anion. Polyatomic ions are ions composed of several atoms per ion. They can be either diatomic ions, triatomic ions and vice versa. There is an uncountable number of known polyatomic ions. Some of these are present in the biological system; some are naturally occurring ions whereas others are synthetic ions. They are very useful polyatomic ions. Atoms in the polyatomic ion are covalently bonded to each other.
There can be sigma bonds as well as pi bonds. Sometimes, a polyatomic ion is formed as a coordination complex. Here, a central metal is surrounded by neutrally charged ligands. These ligands are bonded to the central metal ion via coordinate covalent bonds. Then the complex is considered as a complex ion. Anions in this group containing oxygen are referred to as oxyanions and are all named with an -ate or -ite ending. The most common oxyanion of an element is giving the -ate ending.
NO 3 - nitr ate SO 4 2- sulf ate. CO 3 2- carbon ate PO 4 3- phosph ate. ClO 3 - chlor ate BrO 3 - brom ate. An element may have two or more naturally occurring oxyanions and a system of prefixes and suffixes are used to indicate the number of oxygens contained in the oxyanion relative to the reference -ate oxyanion of the element.
Ionic compounds consist of cations and anions which are attracted to one another forming a compound by association which has a neutral charge overall. The ions in an ionic compound are separate distinct species which is important to their behavior and their chemistry.
Like the separate and distinct nature of the ions which compose an ionic compound, we name ionic compounds by simply naming the cation s and then naming the anion s.
No reference or indication of the number either type of ion is necessary in the name since the lowest whole number of each ion necessary to produce a neutral is used. In naming ionic compounds it becomes clear that knowing the charges of the anions is extremely important to recognizing the charge on those metal ions which could have more than one possibility.
Remember that the compound must be neutral. Occasionally, a compound may be what is known as a double-salt. This is an ionic compound in which there are two different cations present.
These double-salts are not uncommon so it is advantageous to be familiar with their naming. Common double-salts are the salts of hydrogen carbonate, hydrogen sulfate, hydrogen phosphate, and dihydrogen phosphate.
Anions can be considered to be derived from acids, which are covalent molecular compounds which, in water, separate into hydrogen ions and the corresponding anions. The formula of the parent acid is readily found by adding sufficient hydrogen ions to the anion to produce a neutral compound. The simplest anions, the monatomic anions, with an -ide ending are derived from hydro- root -ic acids. Note that cyanide is the only non-monatomic anion whose corresponding acid falls into this category.
It is important to note that the roots for sulfur and phosphorous are different for ions and acids.
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