Chemical formulas

FORMULAS

A formula is a symbol, or a group of symbols that represents a substance. The symbols in a chemical formula identify the elements present in the substance.

EXAMPLES

Thus NaCl is the formula for sodium chloride (common table salt) and so identifies the elements sodium and chlorine as the constituents of salt.


H₂0, tells us that each molecule contains two atoms of hyrdogen and one atom of oxygen, or that there are two atoms of Hydrogen, and one atom of Oxygen. In other words that there are two atoms of hydrogen per one atom of oxygen (2 atoms H / 1 atom O)


The formula for aluminum sulfate, Al₂(SO₄)₃, specifies two atoms of Aluminium, Al, for each three sulfate, SO₄, groups. Each sulfate group contains one atom of sulfur and four atoms of oxygen. Hence, the formula shows a total of two atoms of aluminum, three atoms of sulfur, and twelve atoms of oxygen.

MOLECULAR FORMULAS

A molecular formula gives the actual numbers of atoms of ecah element in a molecule. This is called an Empirical Formula For example water where the formula shows that there are 2 atoms of hydrogen and one atom of oxygen. Since the simplest ratio of hydrogen atoms to oxygen atoms in water is 2 to 1, the empirical formula is also H₂O. The molecular formula of benzene, C₆H₆, identifies the benzene is one carbon atom per one hydrogen atom. Thus the empirical formula of benzene is CH.

Many compounds do not contain discrete molecules but instead are composed of particles called ions. Ions are atoms or groups of atoms that are electrically charged. They usually arise in the combination of a metal and a nonmetal. Thus the composition of compounds such as NaCl, Al₂(SO₄)₃, KOH, and CuSO₄ cannot by identified in terms of the nubmer of atoms of each type in a molecule, but only in terms of a formula unit, as such compounds do not contain physically distinct and electrically neutral molecules.

The molecular formula of the most common form of sulfur is S₈, showing that each molecule of this element consists of eight atoms. The molecular formulas for elemental hyrogen and oxygen are H₂ and O₂, while the formula for neon is Ne. Note that H₂ and 2H do not mean the same thing. H₂ represents a molecule of hydrogen consisting of two atoms of the element, chemically combined. The expression 2H, on the other hand, is that the two hydrogen atoms are not in combination as a unit but are separate particles.A formula is a single symbol or a group of symbols that represents a substance. The symbols in a chemical formula identify the elements present in the substance. Thus NaCl is the formula for sodium chloride (common table salt) and so identifies the elements sodium and chlorine as the constituents of salt.

SUBSCRIPTS

Subscripts are used in formulas to indicate the relative numbers of atoms of each type in the compond, but only if more than one atom of a given element is there. The formula for water, H₂0, tells us that each molecule contains two atoms of hyrdogen and one atom of oxygen, or that there are two atoms of Hydrogen, and one atom of Oxygen. In other words that there are two atoms of hydrogen per one atom of oxygen (2 atoms H / 1 atom O)

The formula of sodium chloride, NaCl, indicates the presence of equal numbers of atoms of the elements sodium and chlorine (1 atom Na / 1 atom Cl). Note that in the formulas for water and sodium chloride the subscript 1 is omitted, which is the usual practice.

The formula for aluminum sulfate, Al₂(SO₄)₃, specifies two atoms of Aluminium, Al, for each three sulfate, SO₄, groups. Each sulfate group contains one atom of sulfur and four atoms of oxygen. Hence, the formula shows a total of two atoms of aluminum, three atoms of sulfur, and twelve atoms of oxygen.






Chemical Compound List 
 
The list of Chemical Compound Formulas are given below.

S.No	Name of the chemical compound	Formula
1	Acetic acid formula	CH3COOH
2	Hydrochloric acid formula	HCl
3	Sulfuric acid formula	H2SO4
4	Acetate formula	CH3COO-
5	Ammonia formula	NH3
6	Nitric acid formula	HNO3
7	Phosphoric acid formula	H3PO4
8	Sodium phosphate formula	Na3PO4
9	Calcium carbonate formula	CaCO3
10	Ammonium sulfate formula	(NH4)2SO4
11	Carbonic acid formula	H2CO3
12	Sodium bicarbonate formula	NaHCO3
13	Sodium hydroxide formula	NaOH
14	Calcium hydroxide formula	Ca(OH)2
15	Ethanol formula	C2H5OH
16	Hydrobromic acid formula	HBr
17	Hydrosulfuric acid formula	H2SO4
18	Nitrous acid formula	HNO2
19	Potassium phosphate formula	KH2PO4
20	Silver nitrate formula	AgNO3
21	Sodium carbonate formula	Na2CO3
22	Sodium chloride formula	NaCl
23	Aaluminum hydroxide formula	Al(OH)3
24	Magnesium hydroxide formula	Mg(OH)3
25	Methane formula	CH4
26	Nitrogen monoxide formula	NO
27	Potassium hydroxide formula	KOH
28	Sodium nitrate formula	NaNO3
29	Sulfurous acid formula	H2SO3
30	Phosphate formula	PO4-
31	Aluminum oxide formula	Al2O3
32	Ammonia chemical formula	NH4
33	Ammonium nitrate formula	NH4NO3
34	Ammonium phosphate formula	(NH4)3PO4
35	Barium hydroxide formula	Ba(OH)2
36	Carbon tetrachloride formula	CCl4
37	Citric acid formula	C6H8O7
38	Hydrocyanic acid formula	HCN
39	Hydrofluoric acid formula	HF
40	Hydroiodic acid formula	HI
41	Hypochlorous acid formula	HClO
42	Iron iii oxide formula	Fe2O3
43	Magnesium phosphate formula	Mg3(PO4)2
44	Sodium acetate formula	C2H3NaO2
45	Sodium sulfate formula	Na2SO4
46	Sucrose formula	C12H22O11
47	Potassium nitrate formula	KNO3
48	Ammonium carbonate formula	(NH4)2CO3
49	Ammonium chloride formula	NH4Cl
50	Ammonium hydroxide formula	NH4OH
51	Calcium nitrate formula	Ca(NO3)2
52	Calcium oxide formula	CaO
53	Carbon monoxide formula	CO
54	Chlorine gas formula	Cl2
55	Hydrogen gas formula	H2
56	Hydrogen peroxide formula	H2O2
57	Hydroxide formula	OH-
58	Magnesium chloride formula	MgCl2
59	Magnesium oxide formula	MgO
60	Potassium chloride formula	KCl
61	Potassium iodide formula	KI
62	Sulfur dioxide formula	SO2
63	Vinegar chemical formula	C2H4O2
64	Ammonium sulfide formula	(NH4)2S
65	Barium nitrate formula	Ba(NO3)2
66	Calcium acetate formula	Ca(COO-)2
67	Chlorous acid formula	HClO2
68	Iron oxide formula	Fe2O3
69	Potassium carbonate formula	K2CO3
70	Silver chloride formula	AgCl
71	Sodium iodide formula	NaI
72	Sodium oxide formula	Na2O
73	Sodium sulfide formula	Na2S
74	Sugar chemical formula	C12H22O11
75	Zinc nitrate formula	Zn(NO3)2
76	Aluminum chloride formula	AlCl3
77	Barium chloride formula	BaCl2
78	Magnesium nitrate formula	Mg(NO3)2
79	Silicon dioxide formula	SiO2
80	Acetone formula	C3H6O
81	Aluminum acetate formula	Al2O(C2H3O2)4
82	Aluminum bromide formula	AlBr3
83	Ammonium acetate formula	C2H3O2NH4
84	Barium phosphate formula	Ba3O8P2
85	Barium sulfate formula	BaSO4
86	Benzene formula	C6H6
87	Bicarbonate formula	CHO3-
88	Chromate formula	CrO42-
89	Copper ii nitrate formula	Cu(NO3)2
90	Cyanide formula	CN-
91	Iron iii hydroxide formula	HFeO2
92	Magnesium sulfate formula	MgSO4
93	Methanol formula	CH3OH
94	Nitrogen dioxide formula	NO2
95	Oxygen gas formula	O2
96	Barium acetate formula	Ba(C2H3O2)2
97	Sodium sulfite formula	Na2SO3
98	Sulfur trioxide formula	SO3
99	Aluminum phosphate formula	AlPO4
100	Bromic acid formula	HBrO3
101	Dinitrogen monoxide formula	N2O
102	Formula for carbon monoxide	CO
103	Formula for carbonic acid	H2CO3
104	Formula for sodium carbonate	Na2CO3
105	Iron ii oxide formula	FeO
106	Lithium phosphate formula	Li3PO4
107	Oxalic acid formula	H2C2O4
108	Potassium dichromate formula	K2Cr2O7
109	Salicylic acid formula	C7H6O3
110	Sodium bromide formula	NaBr
111	Sodium hypochlorite formula	NaClO
112	Zinc acetate formula	Zn(O2CCH3)2
113	Zinc chloride formula	ZnCl2
114	Zinc hydroxide formula	Zn(OH)2
115	Magnesium bicarbonate formula	MgCO3
116	Potassium chlorate formula	KClO3
117	Aluminum carbonate formula	Al2(CO3)3
118	Ascorbic acid formula	C6H8O6
119	Benzoic acid formula	C7H6O2
120	Butane formula	C4H10
121	Chlorine formula	Cl2
122	Formula for ammonium nitrate	(NH4)(NO3)
123	Formula for ammonium phosphate	(NH4)3PO4
124	Formula for carbon tetrachloride	CCl4
125	Formula for nitrous acid	HNO2
126	Formula for potassium phosphate	KH2PO4
129	Hydrogen carbonate formula	CHO3-
130	Hypochlorite formula	NaClO
131	Lead nitrate formula	Pb(NO3)2
132	Magnesium carbonate formula	MgCO3
133	Magnesium nitride formula	Mg3N2
134	Nitrite formula	NO2−
135	Perbromic acid formula	HBrO4
136	Phosphate chemical formula	PO43-
137	Phosphorus trichloride formula	PCl3
138	Potassium acetate formula	CH3CO2K
139	Potassium chromate formula	CrK2O4
140	Zinc sulfate formula	ZnSO4
141	Iodine formula	I2
142	Permanganate ion formula	MnO4-
143	Aluminum formula	Al
144	Aluminum iodide formula	AlI3
145	Calcium bromide formula	CaBr2
146	Chemical formula for citric acid	C6H8O7
147	Chlorate formula	ClO-3
148	Chromic acid formula	H2CrO4
149	Dihydrogen monoxide formula	H2O
150	Dinitrogen pentoxide formula	N2O5
151	Formula for hydrofluoric acid	HF
152	Hexane formula	C6H14
153	Hydrogen phosphate formula	H3PO4
154	Iodic acid formula	HIO3
155	Iron ii nitrate formula	Fe(NO3)3
156	Iron iii carbonate formula	Fe2(CO3)3
157	Lactic acid formula	C3H6O3
158	Lead acetate formula	Pb(C2H3O2)2
159	Lead iv oxide formula	PbO2
160	Lithium hydroxide formula	LiOH
161	Magnesium acetate formula	Mg(CH3COO)2
162	Phosphorus pentachloride formula	PCl5
163	Potassium oxide formula	K2O
164	Potassium phosphate chemical formula	KH2PO4
165	Silver acetate formula	AgC2H3O2
166	Sodium citrate formula	Na3C6H5O7
167	Sodium fluoride formula	NaF
168	Sodium nitrite formula	NaNO2
169	Sulfate ion formula	SO42−
170	Barium oxide formula	BaO
171	Calcium iodide formula	CaI2
172	Hydrogen sulfate formula	HSO4-
173	Lithium oxide formula	Li2O
174	Nitride formula	N3
175	Permanganate formula	KMnO4
176	Silver phosphate formula	Ag3PO4
177	Sodium carbonate chemical formula	Na2CO3
178	Ammonium bromide formula	NH4Br
179	Chemical formula for calcium phosphate	Ca3(PO4)2
180	Dichromate formula	K2Cr2O7
181	Formula for aluminum sulfide	Al2S3
182	Formula for ammonium carbonate	(NH4)2CO3
183	Formula for barium chloride	BaCl2
184	Formula for calcium nitrate	Ca(NO3)2
185	Formula for hydroiodic acid	HI
186	Formula for nitrogen monoxide	NO
187	Formula for potassium carbonate	K2CO3
188	Formula for potassium iodide	KI
189	Formula for potassium nitrate	KNO3
190	Formula for sodium oxide	Na2O
191	Fructose chemical formula	C6H12O6
192	Magnesium iodide formula	MgI2
193	Magnesium sulfide formula	MgS
194	Ozone formula	O3
195	Potassium cyanide formula	KCN
196	Silver oxide formula	Ag2O
197	Sodium chromate formula	Na2CrO4
198	Sodium peroxide formula	Na2O2
199	Toluene formula	C7H8
200	Zinc carbonate formula	ZnCO3
201	Zinc phosphate formula	Zn3(PO4)2
202	Zinc sulfide formula	ZnS
203	Amino acid formula	R(NH2)-COOH
204	Boric acid formula	H3BO3
206	Formula for magnesium phosphate	Mg3(PO4)2
207	Oxalate formula	C2O42−
208	Potassium bicarbonate formula	KHCO3
209	Potassium hypochlorite formula	KClO3
210	Potassium nitrite formula	KNO2
211	Ammonium bicarbonate formula	NH4HCO3
212	Ammonium iodide formula	NH4I
213	Ammonium nitrate chemical formula	(NH4)(NO3)
214	Ammonium nitrite formula	NH4NO2
215	Ammonium oxide formula	(NH4)2O
216	Argon gas formula	Ar
217	Barium bromide formula	BaBr2
218	Barium iodide formula	BaI2
219	Bromate formula	Br
220	Dinitrogen trioxide formula	N2O3
221	Ethylene glycol formula	C2H6O2
222	Formula for hypochlorous acid	HClO
223	Formula for magnesium nitrate	MgNO3
224	Helium gas formula	He
225	Iodide formula	I2
226	Lead ii acetate formula	Pb(C2H3O2)2
227	Lithium chloride formula	LiCl2
228	Phosphate ion formula	PO43-
229	Potassium fluoride formula	KF
230	Potassium sulfite formula	K2SO3
231	Silver carbonate formula	Ag2CO3
232	Sodium cyanide formula	NaCN
233	Sodium nitride formula	Na3N
234	Strontium chloride formula	SrCl2
235	Strontium nitrate formula	Sr(NO3)2
236	Urea formula	CH4N2O
237	Bleach formula	NaClO
238	Chemical formula for carbonic acid	H2CO3
239	Lithium bromide formula	LiBr
240	Aluminum fluoride formula	AlF3
241	Barium fluoride formula	BaF2
242	Butanoic acid formula	C4H8O2
243	Calcium hydride formula	CaH2
245	Copper ii carbonate formula	CuCO3
246	Ethanol structural formula	CH3CH2OH
247	Fluorine gas formula	F2
248	Formula for lithium phosphate	Li3PO4
249	Glycerol formula	C3H8O3
250	Hypobromous acid formula	HBrO
251	Hypoiodous acid formula	HIO
252	Lead iodide formula	PbI2
253	Lithium iodide formula	LiI2
254	Magnesium oxide chemical formula	MgO
255	Magnesium phosphate chemical formula	Mg3PO4
256	Nickel nitrate formula	Ni(NO3)2
257	Potassium chloride chemical formula	KCl
258	Potassium nitrate chemical formula	KNO3
259	Sodium dichromate formula	Na2Cr2O7
260	Sodium nitrate chemical formula	NaNO3
261	Tartaric acid formula	C4H6O6
262	Zinc iodide formula	ZnI2
263	Bromine gas formula	Br2
264	Formula for aluminum bromide	AlBr3
265	Formula for barium sulfate	BaSO4
267	Nickel acetate formula	Ni(C2H3O2)2

List of Organic Compounds

The common and IUPAC names of the organic compounds in the order of their functional groups are given in a tabular form below:

Alkanes

Structure	Common name	IUPAC name
CH3-CH2-CH2-CH3	n-Butane	Butane
(CH3)2CH CH3	iso-Butane	2-methyl propane
CH3(CH2)4CH3	n-hexane	Hexane
CH3.(CH3)2.C.CH3	neo pentane	2,2-di methyl propane
CH4	methane	methane
CH3-CH3	Ethane	Ethane
CH3-CH2-CH3	Propane	Propane

Alkenes

CH2=CH2	Ethylene	Ethene
CH3-CH=CH2	Propylene	Propene
CH3-CH2-CH=CH2	Unsym butylene	1-butene
CH3-CH=CH-CH3	Sym butene	2-butene

Alkynes

H-C≡C-H	Acetylene	Ethyne
CH3-C≡C-H	Methyl acetylene/ Propylene	Propyne
CH3-CH2-C≡C-H	Ethyl acetylene/ Butylene	1-butyne
CH3-C≡C-CH3	Di methyl acetylene Butylene	2-butyne

Alcohols

CH3-OH	Methyl alcohol	Methanol
CH3-CH2-OH	Ethyl alcohol	Ethanol
CH3-CH2-CH2-OH	n- Propyl alcohol	Propanol
CH3-CH(OH)-CH3	iso-propyl alcohol	1-propanol

Ethers

CH3-O-CH3	Dimethyl ether	Methoxy methane
CH3-CH2-O-CH2-CH3	Diethyl ether	Ethoxy ethane
CH3-O-CH2-CH3	Ethylmethylether	methoxy ethane

Aldehydes

HCHO	Formaldehyde	Methanal
CH3CHO	Acetaldehyde	Ethanal
CH3-CH2-CHO	Propanaldehyde	Propanal

Ketones

CH3COCH3	Acetone	Propanone
CH3-CH2-CO-CH3	Ethyl methyl ketone	Butanone

Carboxylic acids

HCOOH	Formic acid	Methanoic acid
CH3COOH	Acetic Acid	Ethanoic acid
CH3-CH2COOH	Propionic acid	Propanoic acid
CH3-CH2-CH2-COOH	n-butyric acid	Butanoic acid

Esters

H-CO-OCH3	Methyl formate	Methyl methanoate
CH3-CO-OCH2-CH3	Ethyl acetate	Ethyl ethanoate

Alkyl halides

CH3-Cl	Methyl chloride	Chloromethane
CH3-CH2-Br	Ethyl bromide	Bromoehtane

Acid Chloride

H-COCl	Formyl chloride	Methanoyl chloride
CH3-COCl	Acetyl chloride	Ethanoyl chloride

Acid amides

H-CO-NH2	Formamide	Methanamide
CH3-CO-NH2	Acetamide	Ethanamide

Amines (Primary)

CH3-NH2	Methyl amine	Methanamine
CH3-CH2-NH2	Ethyl amine	Ethanamine

Amines (Secondary)

(CH3)2-NH	Di methyl amine	N-methyl methanamine
CH3-CH2-(CH3)-NH	Ethyl methyl amine	N-methylethanamine

Amines (Tertiary)

(CH3)3N	tri methyl amine	N,N-dimethyl methanamine
CH3-CH2(CH3)2N	Ethyl dimethyl amine	N,N-dimethyl ethanamine

Other common names for compounds:

C₆H₆(Benzene), C₆H₅.OH (Phenol) C₆H₅.NH₂ ( Aniline), C₆H₅.CH₃( Toluene) C₆H₅COOH(Benzoic acid) C₁₂H₂₂O₁₁(Sucrose).

Many other compounds have names, still in use, which are not in connivance with IUPAC guidelines but accepted, e.g., Camphor, Naphthalene, Anthracene, Isoprene, etc.

Root words indicate the number of carbon atoms in the main chain like meth, eth, prop, dec, etc.

No. of C atoms	Root	No of C atoms	Root	No of C atoms	Root
1	Meth	2	Et	3	Prop
4	But	5	Pent	6	Hex
7	Hept	8	Oct	9	Non
10	Dec	11	Undec	12	Dodec
13	Trindec	14	Tetradec	20	Eicossa

Suffix is further divided into primary suffix and secondary suffix. Primary suffix indicates the saturation or unsaturation like -ene for alkene, present in the compound. If there are more than one, double or triple bonds, this is also mentioned as di, tri, tetra, etc.
Example: CH₂=CH-CH₂-CH=CH₂ is 1,4-pentadiene.Secondary suffix indicates the functional group present in the compound.

The functional groups are mentioned as follows :

• Alcohol -ol
• Aldehyde -al
• Ketone -one
• Carboxylic acid -oic acid
• Ester -oate
• Acid chloride -oyl chloride
• Alkyl cyanide -nitrile etc..

Groups like amine, amide nitro are used completely. For compounds with multiple functional groups a preferential system is designed.
The order of preference will be Acid, Acid ester, acid halide, acid amide, cyanide, aldehyde, ketone, amine, alcohol, ether, alkene, alkylhalide and branched chain. The functional groups are named in this order with the higher placed one taking preference.

In the case of the compounds, the term cyclo is added before the root word like 2-methyl cyclohexene. Aromatic compounds like benzene, toluene will retain their common names in their substituted compounds.

Chemical formulas re designations of molecules and compounds in shorthand notation, similar to that used in Algebra.
Shorthand for elements
Elements can be written as abbreviations or in a shorthand notation. For example, He denotes helium, Fe denotes iron, and Cl denotes chlorine. A chemical formula is writing the elements of a compound, using their abbreviations.
Designation of a molecule
The combination of two or more elements to form a molecule is designated by writing their abbreviations next to each other. For example carbon monoxide is written as CO. The order in which the elements are written is typically alphabetical, but there are a number of exceptions for historical reasons and to clarify the geometry of the molecule.
Number of atoms in a molecule
If there is more than one atom of a type in the molecule, the formula shows it by a small number after the symbol.
For example, water is H2O, which means there are 2 atoms of hydrogen and one atom of oxygen in the molecule.
Carbon dioxide is CO2, which means there is one atom of carbon and two atoms of oxygen in the molecule.
Number of molecules
To show the number of molecules, a full sized number is located in front of the molecule. For example 4 molecules of carbon dioxide is designated as:
4CO2
This means there are a total of 4 C atoms and 8 O atoms in the combination. A way to remember this--taken from Algebra--is to think of it as 4 x (CO2).
Complex formulas
Just as in Algebra, you can use parentheses to separate parts in a complex formula. One example is the formula for nitroglycerin, a highly explosive substance.
C3H5(NO3)3
This formula shows that nitroglycerin consists of 3 atoms of C, 5 atoms of H and then 3 NO3 nitrate ions. If the parentheses were not used, you might have a formula like:
C3H5N3O9
The number of atoms for each element would be correct, but it wouldn't help to describe the true structure of the nitroglycerin molecule.
Chemical Formulas
Chemical formulas such as HClO4 can be divided into empirical formula, molecular formula, and structural formula.
Chemical symbols of elements in the chemical formula represent the elements present, and subscript numbers represent mole proportions of the proceeding elements. Note that no subscript number means a subscript of 1.
From a chemical point of view, an element contained in the substance is a fundamental question, and we represent the elemental composition by a chemical formula, such as H2O for water. This formula implies that the water molecules consist of 2 hydrogen, and 1 oxygen atoms. The formula H2O is also the molecular formula of water. For non-molecular substances such as table salt, we represent the composition with an empirical formula. Sodium chloride is represented by NaCl, meaning that sodium and chlorine ratio in sodium chloride is 1 to 1. Again, the subscript 1 is omitted. Since table salt is an ionic compound, the formula implies that numbers of Na+ ions, and Cl- ions are the same in the solid. The subscript numbers in an empirical formula should have no common divisor.
H H
| |
H-C-C-O-H
| |
H H
Structural of
CH3CH2OH A 3-Dimensional
structure of C6H12
A structural formula reflects the bonding of atoms in a molecule or ion. For example, ethanol can be represented by CH3CH2OH. This is a simple way of representing a more elaborated structure shown on your left. Molecular structures are often beautiful, but the representation is an artwork. For example, a 3-dimensional structure of cyclohexane is shown on the right. This is a chair form, and another structure has a boat form. You will learn more about it in organic chemistry. The molecular formula of benzene is C6H6, and its empirical formula is CH.
You may refer to a substance by its name, and recognize it by its properties. Properties are related to the structure and the composition of the molecules. Knowing the chemical formula is a giant step towards understanding a substance.
Weak Acids and Bases
Weak acids and bases are only partially ionized in their solutions, whereas strong acids and bases are completely ionized when dissolve in water.
Common Weak Acids
Acid Formula
Formic HCOOH
Acetic CH3COOH
Trichloroacetic CCl3COOH
Hydrofluoric HF
Hydrocyanic HCN
Hydrogen
sulfide H2S
Water H2O
Conjugate acids of weak bases NH4+
Common Weak Bases Base Formula
ammonia NH3
trimethyl
ammonia N(CH3)3
pyridine C5H5N
ammonium
hydroxide NH4OH
water H2O
HS- ion HS-
conjugate bases of weak acids e.g.:
HCOO-
Some common weak acids and bases are given here. Furthermore, weak acids and bases are very common, and we encounter them often both in the academic problems and in everyday life.
The ionization of weak acids and bases is a chemical equilibrium phenomenon. The equilibrium principles are essential for the understanding of equilibria of weak acids and weak bases.
The conjugate acid-base pairs have been discussed in Acids and Bases. In this connection, you probably realize that conjugate acids of weak bases are weak acids and conjugate bases of weak acids are weak bases. Ionization of Week Acids H O | //
H--C--C | \\ H O-
Acetic acid, CH3COOH, is a typical weak acid, and it is the ingradient of vinegar. It is partially ionized in its solution.
CH3COOH = CH3COO- + H+
The structure of the acetate ion, CH3COO-, is shown on the right.
Chemical formulas and oxidation numbers
What is the chemical formula for sodium chloride?
A sodium atom will form an ionic bond with a chlorine atom to make a molecule of sodium chloride. Because sodium chloride is a compound made out of ions, it is called an ionic compound
. The chemical formula for sodium chloride is NaCl.
This formula indicates that every molecule of sodium chloride contains one atom of sodium and one atom of chlorine, a 1:1 ratio.
Why do sodium and chlorine combine in a 1:1 ratio? When sodium loses one electron, it becomes an ion with a charge of +1. When chlorine gains an electron, it becomes an ion with a charge of -1. When these two ions combine to form an ionic bond, the net electrical charge is zero. This is because (+1) + (-1) = 0.
All compounds have an electrical charge of zero; that is, they are neutral.
Oxidation numbers
A sodium atom always ionizes to become Na+ (a charge of +1) when it combines with other atoms to make a compound. Therefore, we say that sodium has an oxidation number of 1+ .
An oxidation number indicates how many electrons are lost, gained, or shared when bonding occurs. Notice that the convention for writing oxidation numbers is the opposite of the convention for writing the charge. When writing the oxidation number, the positive (or negative) symbol is written after the number, not before it.
What is chlorine’s oxidation number? If you think it is 1-, you are right. This is because chlorine gains one electron, one negative charge, when it bonds with other atoms.
Predicting oxidation numbers from the periodic table
Here you can tell how many valence electrons an element has by its placement on the periodic table. If you can determine how many valence electrons an element has, you can predict its oxidation number. For example, locate beryllium (Be) on the periodic table below. It is in the second column, or Group 2, which means beryllium has two valence electrons. Will beryllium get rid of two electrons, or gain six in order to obtain a stable octet? Of course, it is easier to lose two electrons. When these two electrons are lost, beryllium becomes an ion with a charge of +2. Therefore, the most common oxidation number for beryllium is 2+. In fact, the most common oxidation number for all elements in Group 2 is 2+.
Writing the chemical formulas of ionic compounds.
Monoatomic ions
Both sodium and chlorine ions are monoatomic ions , that is, ions that consist of a single atom. It’s easy to write the chemical formula for compounds made of monatomic ions, if you follow these rules: Some elements have more than one oxidation number. In this case, roman numerals are used to distinguish the oxidation number. Figure 19.17 shows a few of these elements.
Example: Writing a chemical formula
Write the formula for a compound that is made of iron (III) and oxygen.
1. Find the oxidation numbers of each element in the compound. Iron (III) is a transition metal. The roman numbers indicate that it has an oxidation number of 3+. Its formula is Fe
3+ .
Oxygen is in group 18 of the periodic table and has an oxidation number of 2-. Its formula is O
2- .
2. Determine the ratios of each element and write the chemical formula.
If one iron (III) ion bonds with one oxygen ion, will the compound be neutral? No, since 3+ added to 2- equals 1+. If you have two iron (III) ions for every three oxygen ions, what happens? 2(3+) added to 3(2-) is equal to 0. This means that three iron (III) ions bond with two oxygen ions to get a neutral compound.
The formula for a compound of iron (III) and oxygen is Fe
2
O
3
Ionic compounds made of more than two types of atoms
Have you ever taken an antacid for an upset stomach? Many antacids contain calcium carbonate, or CaCO 3 . How many types of atoms does this compound contain? You are right if you said three: calcium, carbon, and oxygen. Some ionic compounds contain polyatomic ions . Polyatomic ions contain more than one type of atom. The prefix poly means “many.” Table lists some common polyatomic ions.







Symbols and Charges for Monoatomic Ions


Symbol Name Symbol Name
H+ hydrogen ion H- hydride
Li+ lithium ion F- fluoride
Na+ sodium ion Cl- chloride
K+ potassium ion Br- bromide
Rb+ rubidium ion I- iodide
Cs+ cesium ion O2- oxide
Be2+ beryllium ion S2- sulfide
Mg2+ magnesium ion Se2- selenide
Ca2+ calcium ion Te2- telluride
Sr2+ strontium ion N3- nitride
Ba2+ barium ion P3- phosphide
Ra2+ radium ion As3- arsenide
Ag+ silver ion Ni2+ nickel ion
Zn2+ zinc ion Al3+ aluminum ion
Symbols and Charges for Monoatomic Ions
Systematic name Common Systematic name Common
Symbol (Stock system) name Symbol (Stock system) name
Cu+ copper(I) cuprous Hg22+ mercury(I) mercurous
Cu2+ copper(II) cupric Hg2+ mercury(II) mercuric
Fe2+ iron(II) ferrous Pb2+ lead(II) plumbous
Fe3+ iron(III) ferric Pb4+ lead(IV) plumbic
Sn2+ tin(II) stannous Co2+ cobalt(II) cobaltous
Sn4+ tin(IV) stannic Co3+ cobalt(III) cobaltic
Cr2+ chromium(II) chromous Au+ gold(I) aurous
Cr3+ chromium(III) chromic Au3+ gold(III) auric
Mn2+ manganese(II) manganous
Mn3+ manganese(III) manganic
Symbols and Charges for Polyatomic Ions
Formula Name Formula Name
NO3- nitrate ClO4- perchlorate
NO2- nitrite ClO3- chlorate
CrO42- chromate ClO2- chlorite
Cr2O72- dichromate ClO- hypochlorite
CN- cyanide IO4- periodate
MnO4- permanganate IO3- iodate
OH- hydroxide IO- hypoiodite
O22- peroxide BrO3- bromate
NH2- amide BrO- hypobromite
CO32- carbonate HCO3- hydrogen carbonate (bicarbonate)
SO42- sulfate HSO4- hydrogen sulfate (bisulfate)
SO32- sulfite HSO3- hydrogen sulfite (bisulfite)
C2O42- oxalate HC2O4- hydrogen oxalate (binoxalate)
PO43- phosphate HPO42- hydrogen phosphate
PO33- phosphite H2PO4- dihydrogen phosphate
S2O32- thiosulfate HS- hydrogen sulfide
AsO43- arsenate BO33- borate
SeO42- selenate B4O72- tetraborate
SiO32- silicate SiF62- hexafluorosilicate
C4H4O62- tartrate SCN- thiocyanate
C2H3O2- acetate (an alternate way to write acetate is CH3COO-)
There is one positive polyatomic ion. It is NH4+ and is called the ammonium ion.

Molecular formulas can be calculated using empirical formulas:

• Given that the empirical formula of a compound is CH and the molar mass is 104 g/mol, calculate the molecular formula.
  mass of C  =  12.0 g/mol
  mas of H  =   1.01 g/mol
  empirical formula mass  =   13.0 g/mol
• to find the number of CH units in the compound:
• # CH units  =   (104 g/mol)(1 mol/13.0 g)  =   8.00
• Molecular formula  =   8(CH) or C₈H₈

Empirical formulas can be calculated using experimental data:

Given that a certain compound is 69.58% Ba, 6.090% C and 24.32% O, calculate the empirical formula of this compound.

Assume that you have 100.00 g of the compound:

• 69.58%  Ba  =  69.58 g Ba
• 6.090% C  =   6.090 g C
• 24.32% O  =   24.32 g O

Convert the mass of each element to moles of that element:

• Ba  =  (69.58 g Ba)(1 mol Ba/137.3 g Ba)  =  0.5068 mol Ba
• C  =   (6.090 g C)(1 mol C/12.01 g C)  =   0.5071 mol C
• O  =   (24.32 g O)(1 mol O/16.00 g O)  =   1.520 mol O

Divide through each value by the smallest number of moles to get a 1 : 1.001 : 2.999 ratio, which rounds of nicely to give the formula BaCO₃

Empirical and Molecular Formulas

Believe it or not, there is more than one kind of chemical formula (insert a sharp gasp of surprise here). Judging from the heading of this section, they would be empirical and molecular formulas. Empirical formulas give the lowest whole number ratio of the atoms in a compound, whereas the molecular formula gives the exact composition of one molecule.

Empirical	Molecular
HO	H2O2
CH	C2H2
CH	C6H6
NO	NO
NO2	N2O4

Chemical Names and Formulas

 

A	B
Ammonia	NH3
Carbon dioxide	CO2
Carbon monoxide	CO
Chlorine	Cl2
Hydrogen chloride	HCl
Hydrogen	H2
Hydrogen sulfide	H2S
Methane	CH4
Nitrogen	N2
Nitrogen (II) oxide	NO
Oxygen	O2
Sulfur dioxide	SO2
Aluminun oxide	Al2O3
Barium Sulfate	BaSO4
Calcium hydroxide	Ca(OH)2
Copper (II) sulfate	CuSO4
Ethane	C2H6
Ethene (ethylene)	C2H4
Ethyne (acetylene)	C2H2
Hydrogen fluoride	HF
Hydrogen iodide	HI
Iodine chloride	ICl
Lead (II) oxide	PbO
Magnesium oxide	MgO
Nitrogen (II) oxide	NO
Nitrogen (IV) oxide	NO2
Potassium chloride	KCl
Sodium chloride	NaCl
Sulfur dioxide	SO2
Water	H2O
Aluminum Bromide	AlBr3
Aluminum Carbonate	Al2(CO3)3
Aluminum Chloride	AlCl3
Aluminum Chromate	Al2(CrO4)3
Aluminum Hydroxide	Al(OH)3
Aluminum Iodide	AlI3
Aluminum Nitrate	Al(NO3)3
Aluminum Phosphate	AlPO4
Aluminum Sulfate	Al2(SO4)3
Aluminum Sulfide	Al2S3
Ammonium Acetate	NH4C2H3O2
Ammonium Bromide	NH4Br
Ammonium Carbonate	(NH4)2CO3
Ammonium Chloride	NH4Cl
Ammonium Chromate	(NH4)2CrO4
Ammonium Hydroxide	NH4OH
Ammonium Iodide	NH4I
Ammonium Nitrate	NH4NO3
Ammonium Phosphate	(NH4)3PO4
Ammonium Sulfate	(NH4)2SO4
Ammonium Sulfide	(NH4)2S
Barium Acetate	Ba(C2H3O2)2
Barium Bromide	BaBr2
Barium Carbonate	BaCO3
Barium Chloride	BaCl2
Barium Chromate	BaCrO4
Barium Hydroxide	Ba(OH)2
Barium Iodide	BaI2
Barium Nitrate	Ba(NO3)2
Barium Phosphate	Ba3(PO4)2
Barium Sulfate	BaSO4
Barium Sulfide	BaS
Calcium Acetate	Ca(C2H3O2)2
Calcium Bromide	CaBr2
Calcium Carbonate	CaCO3
Calcium Chloride	CaCl2
Calcium Chromate	CaCrO4
Calcium Hydroxide	Ca(OH)2
Calcium Iodide	CaI2
Calcium Nitrate	Ca(NO3)2
Calcium Phosphate	Ca3(PO4)2
Calcium Sulfate	CaSO4
Calcium Sulfide	CaS
Copper (II) Acetate	Cu(C2H3O2)2
Copper (II) Bromide	CuBr2
Copper (II) Carbonate	CuCO3
Copper (II) Chloride	CuCl2
Copper (II) Chromate	CuCrO4
Copper (II) Hydroxide	Cu(OH)2
Copper (II) Iodide	CuI2
Copper (II) Nitrate	Cu(NO3)2
Copper (II) Phosphate	Cu3(PO4)2
Copper (II) Sulfate	CuSO4
Copper (II) Sulfide	CuS
Iron (II) Acetate	Fe(C2H3O2)2
Iron (II) Bromide	FeBr2
Iron (II) Carbonate	FeCO3
Iron (II) Chloride	FeCl2
Iron (II) Chromate	FeCrO4
Iron (II) Hydroxide	Fe(OH)2
Iron (II) Iodide	FeI2
Iron (II) NItrate	Fe(NO3)2
Iron (II) Phosphate	Fe3(PO4)2
Iron (II) Sulfate	FeSO4
Iron (II) Sulfide	FeS
Iron (III) Acetate	Fe(C2H3O2)3
Iron (III) Bromide	FeBr3
Iron (III) Carbonate	Fe2(CO3)3
Iron (III) Chloride	FeCl3
Iron (III) Chromate	Fe2(CrO4)3
Iron (III) Hydroxide	Fe(OH)3
Iron (III) Iodide	FeI3
Iron (III) Nitate	Fe(NO3)3
Iron (III) Phosphate	FePO4
Iron (III) Sulfate	Fe2(SO4)3
Iron (III) Sulfide	Fe2S3
Magnesium Acetate	Mg(C2H3O2)2
Magnesium Bromide	MgBr2
Magnesium Carbonate	MgCO3
Magnesium Chloride	MgCl2
Magnesium Chromate	MgCrO4
Magnesium Hydroxide	Mg(OH)2
Magnesium Iodide	MgI2
Magnesium Nitrate	Mg(NO3)2
Magnesium Phosphate	Mg3(PO4)2
Magnesium Sulfate	MgSO4
Magnesium Sulfide	MgS
Mercury (I) Acetate	HgC2H3O2
Mercury (I) Bromide	HgBr
Mercury (I) Carbonate	Hg2CO3
Merucry (I) Chloride	HgCl
Mercury (I) Chromate	Hg2CrO4
Merucry (I) Hydroxide	HgOH
Mercury (I) Iodide	HgI
Mercury (I) Nitrate	HgNO3
Mercury (I) Phosphate	Hg3PO4
Mercury (I) Sulfate	Hg2SO4
Mercury (I) Sulfide	Hg2S
Merucry (II) Acetate	Hg(C2H3O2)2
Mercury (II) Bromide	HgBr2
Mercury (II) Carbonate	HgCO3
Merucry (II) Chloride	HgCl2
Mercury (II) Chromate	HgCrO4
Mercury (II) Hydroxide	Hg(OH)2
Mercury (II) Iodide	HgI2
Mercury (II) Nitrate	Hg(NO3)2
Mercury (II) Phosphate	Hg3(PO4)2
Merucry (II) Sulfate	HgSO4
Mercury (II) Sulfide	HgS
Potassium Acetate	KC2H3O2
Potassium Bromide	KBr
Potassium Carbonate	K2CO3
Potassium Chloride	KCl
Potassium Chromate	K2CrO4
Potassium Hydroxide	KOH
Potassium Iodide	KI
Potassium Nitrate	KNO3
Potassium Phosphate	K3PO4
Potassium Sulfate	K2SO4
Potassium Sulfide	K2S
Silver Acetate	AgC2H3O2
Silver Bromide	AgBr
Silver Carbonate	Ag2CO3
Silver Chloride	AgCl
Silver Chromate	Ag2CrO4
Silver Hydroxide	AgOH
Silver Iodide	AgI
Silver Nitrate	AgNO3
Silver Phosphate	Ag3PO4
Silver Sulfate	Ag2SO4
Silver Sulfide	Ag2S
Sodium Acetate	NaC2H3O2
Sodium Bromide	NaBr
Sodium Carbonate	Na2CO3
Sodium Chloride	NaCl
Sodium Chromate	Na2CrO4
Sodium Hydroxide	NaOH
Sodium Iodide	NaI
Sodium Nitrate	NaNO3
Sodium Phosphate	Na3PO4
Sodium Sulfate	Na2SO4
Sodium Sulfide	Na2S
Zinc Acetate	Zn(C2H3O2)2
Zinc Bromide	ZnBr2
Zinc Carbonate	ZnCO3
Zinc Chloride	ZnCl2
Zinc Chromate	ZnCrO4
Zinc Hydroxide	Zn(OH)2
Zinc Iodide	ZnI2
Zinc Nitrate	Zn(NO3)2
Zinc Phosphate	Zn2(PO4)2
Zinc Sulfate	ZnSO4
Zince Sulfide	ZnS
Lead (II) Acetate	Pb(C2H3O2)2
Lead (II) Bromide	PbBr2
Lead (II) Carbonate	PbCO3
Lead (II) Chloride	PbCl2
Lead (II) Chromate	PbCrO4
Lead (II) Hydroxide	Pb(OH)2
Lead (II) Iodide	PbI2
Lead (II) Nitrate	Pb(NO3)2
Lead (II) Phosphate	Pb3(PO4)2
Lead (II) Sulfate	PbSO4
Lead (II) Sulfide	PbS
Lead (IV) Acetate	Pb(C2H3O2)4
Lead (IV) Bromide	PbBr4
Lead (IV) Chromate	Pb(CO3)2
Lead (IV) Hydroxide	Pb(OH)4
Lead (IV) Iodide	PbI4
Lead (IV) Nitrate	Pb(NO3)4
Lead (IV) Phosphate	Pb3(PO4)4
Lead (IV) Sulfate	Pb(SO4)2
Lead (IV) Sulfide	PbS2
Aluminum Acetate	Al(C2H3O2)3