The chemical formula of an ionic compound tells us the ratio of the elements present We can use valency to work out chemical formulae for simple compounds. A chemical formula is an easy way to show how many atoms are in a molecule. A subscript outside a bracket multiplies by all the elements inside the brackets. MS Excel() PDF Format of Chemical Formulas PDF CSV Format of Chemical Formulas CSV Zip of all formats Format of Chemical.
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Why “Systematic Names”? # atomic particles. 3 (p, n, e). # elements. +. # elements in earth's crust (99%). 8. # elements in all living things. # compounds. >. CHEMICAL NOMENCLATURE AND FORMULAE. CHEMICAL FORMULAE. = formulae describing chemical elements, compounds and ions. Molecular formula . Chemical symbols of elements in the chemical formula represent the If you have to multiply by, say, 2 1/2, do so, THEN multiply EVERYTHING on each side of.
What is the Chemical Formula for Zinc Nitrate. Substances may change between these phases of matter with changes in temperature or pressure. What is the Chemical Formula for Water. Chemistry formulas. The formula unit is the absolute grouping of atoms or ions represented by the empirical formula of a compound, either ionic or covalent.
In such cases, it is necessary for the compounds to have different names that distinguish among the possible arrangements. Many compounds, particularly those that have been known for a relatively long time, have more than one name: Like the names of most elements, the common names of chemical compounds generally have historical origins, although they often appear to be unrelated to the compounds of interest.
For example, the systematic name for KNO 3 is potassium nitrate, but its common name is saltpeter. Unfortunately, some chemicals that are widely used in commerce and industry are still known almost exclusively by their common names; in such cases, familiarity with the common name as well as the systematic one is required.
The procedure for naming such compounds is outlined in Figure 3. Place the ions in their proper order: Metals that form only one cation. As noted previosuly, these metals are usually in Groups 1—3, 12, and The name of the cation of a metal that forms only one cation is the same as the name of the metal with the word ion added if the cation is by itself.
Metals that form more than one cation. As shown in Figure 3. This behavior is observed for most transition metals, many actinides, and the heaviest elements of Groups 13— In such cases, the positive charge on the metal is indicated by a roman numeral in parentheses immediately following the name of the metal. An older system of nomenclature for such cations is still widely used, however. For example, on the label of dental fluoride rinse, the compound chemists call tin II fluoride is usually listed as stannous fluoride.
Some examples of metals that form more than one cation are listed in Table 3. Polyatomic cations. The names of the common polyatomic cations that are relatively important in ionic compounds such as, the ammonium ion are in Table 2. Monatomic anions.
Because the charges on these ions can be predicted from their position in the periodic table, it is not necessary to specify the charge in the name. Examples of monatomic anions are in Table 2. Polyatomic anions. Polyatomic anions typically have common names that must be memorized; some examples are in Table 2. Polyatomic anions that contain a single metal or nonmetal atom plus one or more oxygen atoms are called oxoanions or oxyanions.
In cases where only two oxoanions are known for an element, the name of the oxoanion with more oxygen atoms ends in -ate, and the name of the oxoanion with fewer oxygen atoms ends in -ite. The halogens and some of the transition metals form more extensive series of oxoanions with as many as four members.
The relationship between the names of oxoanions and the number of oxygen atoms present is diagrammed in Figure 3. Write the name of the compound as the name of the cation followed by the name of the anion. Figure 3. It is not necessary to indicate the number of cations or anions present per formula unit in the name of an ionic compound because this information is implied by the charges on the ions.
The charge of the ions must be considered when writing the formula for an ionic compound from its name, however. Thus, the formula is CaCl 2. The best way to learn how to name ionic compounds is to work through a few examples, referring to Figure 3.
With only a few exceptions, these metals are usually transition metals or actinides. Most transition metals, many actinides, and the heaviest elements of groups 13—15 can form more than one cation. Write the systematic name and the common name if applicable for each ionic compound. A If only one charge is possible for the cation, give its name, consulting Table 2. If the cation can have more than one charge Table 3.
B If the anion does not contain oxygen, name it according to step 3a, using Table 2. For polyatomic anions that contain oxygen, use Table 2. C Beginning with the cation, write the name of the compound. C Because we begin with the name of the cation, the name of this compound is lithium chloride, which is used medically as an antidepressant drug. A B The cation is the magnesium ion, and the anion, which contains oxygen, is sulfate.
C Because we list the cation first, the name of this compound is magnesium sulfate.
A B The cation is the ammonium ion from Table 2. C The compound is therefore ammonium phosphate, which is widely used as a fertilizer.
It is not necessary to specify that the formula unit contains three ammonium ions because three are required to balance the negative charge on phosphate. A B The cation is a transition metal that often forms more than one cation Table 3. We must therefore specify the positive charge on the cation in the name: The anion is oxide.
C The name of this compound is copper I oxide or, in the older system, cuprous oxide. Copper I oxide is used as a red glaze on ceramics and in antifouling paints to prevent organisms from growing on the bottoms of boats. The bottom of a boat is protected with a red antifouling paint containing copper I oxide, Cu 2 O.
A Identify the cation and its charge using the location of the element in the periodic table and Table 2. B Identify the anion using Table 2. Aluminum sulfate is used to tan leather and purify drinking water. A Because chromium is a transition metal, it can form cations with different charges.
This compound is a common green pigment that has many uses, including camouflage coatings. Ionic compounds are named according to systematic procedures, although common names are widely used.
Ionic compounds are named by writing the cation first, followed by the anion. If a metal can form cations with more than one charge, the charge is indicated by roman numerals in parentheses following the name of the metal.
Oxoanions are polyatomic anions that contain a single metal or nonmetal atom and one or more oxygen atoms.
When chemists synthesize a new compound, they may not yet know its molecular or structural formula. 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 4 H The ratio of carbon atoms to hydrogen atoms in butane is 4: The empirical formula for butane is therefore C 2 H 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 2 H 5 , but it contains two C 2 H 5 formula units, giving a molecular formula of C 4 H 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. If the charges are not the same magnitude, then a cation: Ionic compounds do not contain discrete molecules, so empirical formulas are used to indicate their compositions. An ionic compound that contains only two elements, one present as a cation and one as an anion, is called a binary ionic compound.
One example is MgCl 2 , a coagulant used in the preparation of tofu from soybeans.
For binary ionic compounds, the subscripts in the empirical formula can also be obtained by crossing charges: This method is shown schematically as follows:. Crossing charges. One method for obtaining subscripts in the empirical formula is by crossing charges. Using the absolute values of the charges on the ions as subscripts gives the formula Mg 2 O This simplifies to its correct empirical formula MgO.
Write the empirical formula for the simplest binary ionic compound formed from each ion or element pair. Asked for: Check to make sure the empirical formula is electrically neutral. B Using the absolute values of the charges on the ions as the subscripts gives Ga3As Because we write subscripts only if the number is greater than 1, the empirical formula is GaAs.
GaAs is gallium arsenide, which is widely used in the electronics industry in transistors and other devices. We must therefore find multiples of the charges that cancel.
We cross charges, using the absolute value of the charge on one ion as the subscript for the other ion:. The compound Eu 2 O 3 is neutral. Europium oxide is responsible for the red color in television and computer screens. 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. The subscripts in CaCl 2 cannot be reduced further.
Just as there are many more kinds of molecules than simple elements, there are many more kinds of polyatomic ions than monatomic ions.
Polyatomic anions are much more numerous than polyatomic cations; some common examples are in Table 3. 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.
Write the empirical formula for the compound formed from each ion pair. Many ionic compounds occur as hydrates , compounds that contain specific ratios of loosely bound water molecules, called waters of hydration. Waters of hydration can often be removed simply by heating. For example, calcium dihydrogen phosphate can form a solid that contains one molecule of water per Ca H 2 PO 4 2 unit and is used as a leavening agent in the food industry to cause baked goods to rise.
When heated, all five water molecules are lost, giving a white solid with the empirical formula CuSO 4. Loss of Water from a Hydrate with Heating. Images used with permission from Wikipedia. Compounds that differ only in the numbers of waters of hydration can have very different properties. Similar processes are used in the setting of cement and concrete.
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 3. Prefixes derived from Greek stems are used to indicate the number of each type of atom in the formula unit Table 3. 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 Start with the element at the far left in the periodic table and work to the right. If two or more elements are in the same group, start with the bottom element and work up.
Write the formula for each binary covalent compound. List the elements in the same order as in the formula, use Table 3. There is no complete list of chemical compounds since by nature the list would be infinite.
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