2.8 Naming inorganic compounds – chemistry libretexts usd to kes exchange rate today

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As with ionic compounds, the system for naming covalent compounds enables chemists to write the molecular formula from the name and vice versa. This and the following section describe the rules for naming simple covalent compounds, beginning with inorganic compounds and then turning to simple organic compounds that contain only carbon and hydrogen.

When chemists synthesize a new compound, they may not yet know its molecular or structural formula 1 jpy to usd. In such cases, they usually begin by determining its empirical formula, the relative numbers of atoms of the elements in a compound, reduced to the smallest whole numbers. Because the empirical formula is based on experimental measurements of the numbers of atoms in a sample of the compound, it shows only the ratios of the numbers of the elements present.


The difference between empirical and molecular formulas can be illustrated with butane, a covalent compound used as the fuel in disposable lighters. The molecular formula for butane is C 4H 10. The ratio of carbon atoms to hydrogen atoms in butane is 4:10, which can be reduced to 2:5. The empirical formula for butane is therefore C 2H 5. The formula unit is the absolute grouping of atoms or ions represented by the empirical formula of a compound, either ionic or covalent. Butane has the empirical formula C 2H 5, but it contains two C 2H 5 formula units, giving a molecular formula of C 4H 10.

Because ionic compounds do not contain discrete molecules, empirical formulas are used to indicate their compositions. All compounds, whether ionic or covalent, must be electrically neutral. Consequently, the positive and negative charges in a formula unit must exactly cancel each other usa today coaches poll football. If the cation and the anion have charges of equal magnitude, such as Na + and Cl −, then the compound must have a 1:1 ratio of cations to anions, and the empirical formula must be NaCl. If the charges are not the same magnitude, then a cation:anion ratio other than 1:1 is needed to produce a neutral compound. In the case of Mg 2 + and Cl −, for example, two Cl − ions are needed to balance the two positive charges on each Mg 2 + ion, giving an empirical formula of MgCl 2. Similarly, the formula for the ionic compound that contains Na + and O 2− ions is Na 2O.

The subscript for Eu 3 + is 2 (from O 2−), and the subscript for O 2− is 3 (from Eu 3 +), giving Eu 2O 3; the subscripts cannot be reduced further. The empirical formula contains a positive charge of 2(+3) = +6 and a negative charge of 3(−2) = −6, for a net charge of 0 dollar vs euro chart. The compound Eu 2O 3 is neutral. Europium oxide is responsible for the red color in television and computer screens.

c. A Because the charges on the ions are not given, we must first determine the charges expected for the most common ions derived from calcium and chlorine. Calcium lies in group 2, so it should lose two electrons to form Ca 2 +. Chlorine lies in group 17, so it should gain one electron to form Cl −.

B Two Cl − ions are needed to balance the charge on one Ca 2 + ion, which leads to the empirical formula CaCl 2. We could also cross charges, using the absolute value of the charge on Ca 2 + as the subscript for Cl and the absolute value of the charge on Cl − as the subscript for Ca:

Polyatomic ions are groups of atoms that bear net electrical charges, although the atoms in a polyatomic ion are held together by the same covalent bonds that hold atoms together in molecules usd to inr conversion. Just as there are many more kinds of molecules than simple elements, there are many more kinds of polyatomic ions than monatomic ions. Two examples of polyatomic cations are the ammonium (NH 4 +) and the methylammonium (CH 3NH 3 +) ions. Polyatomic anions are much more numerous than polyatomic cations; some common examples are in Table \(\PageIndex{1}\). Table \(\PageIndex{1}\): Common Polyatomic Ions and Their Names Formula

The method used to predict the empirical formulas for ionic compounds that contain monatomic ions can also be used for compounds that contain polyatomic ions. The overall charge on the cations must balance the overall charge on the anions in the formula unit. Thus, K + and NO 3 − ions combine in a 1:1 ratio to form KNO 3 (potassium nitrate or saltpeter), a major ingredient in black gunpowder. Similarly, Ca 2 + and SO 4 2− form CaSO 4 (calcium sulfate), which combines with varying amounts of water to form gypsum and plaster of Paris. The polyatomic ions NH 4 + and NO 3 − form NH 4NO 3 (ammonium nitrate), a widely used fertilizer and, in the wrong hands, an explosive convert binary. One example of a compound in which the ions have charges of different magnitudes is calcium phosphate, which is composed of Ca 2 + and PO 4 3− ions; it is a major component of bones. The compound is electrically neutral because the ions combine in a ratio of three Ca 2 + ions [3(+2) = +6] for every two ions [2(−3) = −6], giving an empirical formula of Ca 3(PO 4) 2; the parentheses around PO 4 in the empirical formula indicate that it is a polyatomic ion euro today rate in pakistan. Writing the formula for calcium phosphate as Ca 3P 2O 8 gives the correct number of each atom in the formula unit, but it obscures the fact that the compound contains readily identifiable PO 4 3− ions.

Binary covalent compounds—covalent compounds that contain only two elements—are named using a procedure similar to that used for simple ionic compounds, but prefixes are added as needed to indicate the number of atoms of each kind. The procedure, diagrammed in Figure \(\PageIndex{2}\) consists of the following steps:

• The element farthest to the left in the periodic table is usually named first. If both elements are in the same group, the element closer to the bottom of the column is named first.

• The second element is named as if it were a monatomic anion in an ionic compound (even though it is not), with the suffix -ide attached to the root of the element name.

Prefixes derived from Greek stems are used to indicate the number of each type of atom in the formula unit ( Table \(\PageIndex{2}\)). The prefix mono- (“one”) is used only when absolutely necessary to avoid confusion, just as the subscript 1 is omitted when writing molecular formulas.

To demonstrate steps 1 and 2a, HCl is named hydrogen chloride (because hydrogen is to the left of chlorine in the periodic table), and PCl 5 is phosphorus pentachloride. The order of the elements in the name of BrF 3, bromine trifluoride, is determined by the fact that bromine lies below fluorine in Group 17.

• If a molecule contains more than one atom of both elements, then prefixes are used for both. Thus N 2O 3 is dinitrogen trioxide, as shown in Figure 2.13.

• In some names, the final a or o of the prefix is dropped to avoid awkward pronunciation. Thus OsO 4 is osmium tetroxide rather than osmium tetraoxide.

• Binary compounds of the elements with oxygen are generally named as “element oxide,” with prefixes that indicate the number of atoms of each element per formula unit current exchange rate usd to cad. For example, CO is carbon monoxide. The only exception is binary compounds of oxygen with fluorine, which are named as oxygen fluorides.

• Certain compounds are always called by the common names that were assigned before formulas were used. For example, H 2O is water (not dihydrogen oxide); NH 3 is ammonia; PH 3 is phosphine; SiH 4 is silane; and B 2H 6, a dimer of BH 3, is diborane. For many compounds, the systematic name and the common name are both used frequently, requiring familiarity with both 1 usd in inr. For example, the systematic name for NO is nitrogen monoxide, but it is much more commonly called nitric oxide. Similarly, N 2O is usually called nitrous oxide rather than dinitrogen monoxide. Notice that the suffixes – ic and – ous are the same ones used for ionic compounds.

• List the elements in order according to their positions in the periodic table. Identify the number of each type of atom in the chemical formula and then use Table \(\PageIndex{2}\) to determine the prefixes needed.

• A Because sulfur is to the left of fluorine in the periodic table, sulfur is named first. Because there is only one sulfur atom in the formula, no prefix is needed. B There are, however, six fluorine atoms, so we use the prefix for six: hexa- ( Table \(\PageIndex{2}\)). The compound is sulfur hexafluoride.

• A Because nitrogen is to the left of oxygen in the periodic table, nitrogen is named first. Because more than one atom of each element is present, prefixes are needed to indicate the number of atoms of each. According to Table \(\PageIndex{2}\) "Prefixes for Indicating the Number of Atoms in Chemical Names", the prefix for two is di-, and the prefix for four is tetra-. B The compound is dinitrogen tetroxide (omitting the a in tetra- according to step 2c) and is used as a component of some rocket fuels.

• A Although oxygen lies to the left of chlorine in the periodic table, it is not named first because ClO 2 is an oxide of an element other than fluorine (step 3a). Consequently, chlorine is named first, but a prefix is not necessary because each molecule has only one atom of chlorine futures market quotes. B Because there are two oxygen atoms, the compound is a dioxide. Thus the compound is chlorine dioxide. It is widely used as a substitute for chlorine in municipal water treatment plants because, unlike chlorine, it does not react with organic compounds in water to produce potentially toxic chlorinated compounds.

List the elements in the same order as in the formula, use Table \(\PageIndex{2}\) to identify the number of each type of atom present, and then indicate this quantity as a subscript to the right of that element when writing the formula.

• Sulfur has no prefix, which means that each molecule has only one sulfur atom. The prefix tri- indicates that there are three oxygen atoms. The formula is therefore SO 3. Sulfur trioxide is produced industrially in huge amounts as an intermediate in the synthesis of sulfuric acid.

• The prefix di- tells you that each molecule has two iodine atoms, and the prefix penta- indicates that there are five oxygen atoms. The formula is thus I 2O 5, a compound used to remove carbon monoxide from air in respirators.

The structures of some of the compounds in Examples \(\PageIndex{3}\) and \(\PageIndex{4}\) are shown in Figure \(\PageIndex{2}\) along with the location of the “central atom” of each compound in the periodic table. It may seem that the compositions and structures of such compounds are entirely random, but this is not true. After mastering the material discussed later on this course, one is able to predict the compositions and structures of compounds of this type with a high degree of accuracy.

Figure \(\PageIndex{2}\): The Structures of Some Covalent Inorganic Compounds and the Locations of the “Central Atoms” in the Periodic Table. The compositions and structures of covalent inorganic compounds are not random and can be predicted from the locations of the component atoms in the periodic table.

The composition of a compound is represented by an empirical or molecular formula, each consisting of at least one formula unit hulu rates. Covalent inorganic compounds are named using a procedure similar to that used for ionic compounds, whereas hydrocarbons use a system based on the number of bonds between carbon atoms. Covalent inorganic compounds are named by a procedure similar to that used for ionic compounds, using prefixes to indicate the numbers of atoms in the molecular formula. An empirical formula gives the relative numbers of atoms of the elements in a compound, reduced to the lowest whole numbers. The formula unit is the absolute grouping represented by the empirical formula of a compound, either ionic or covalent. Empirical formulas are particularly useful for describing the composition of ionic compounds, which do not contain readily identifiable molecules. Some ionic compounds occur as hydrates, which contain specific ratios of loosely bound water molecules called waters of hydration.


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