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Naming of Compounds

Naming of Compounds.

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Naming of Compounds

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  1. Naming of Compounds Since the overwhelming majority of elements occur in compounds, we must learn how these elements interact, specifically, how the electrons affect each other in compounds. We can do this using symbols, which are combined (chemical formula) to represent the composition of a compound. Additionally we must learn how to name these compounds (chemical nomenclature.) Binary compounds consist of only two elements. Ternary compound consist of more than two elements.

  2. Kinds of Formulas A qualitative analysis of a compound could tell us what elements are present in the compound. Thus, it only shows the ratio of elements in relation to each other. This is represented by an empirical formula. (reduced formula). A quantitative analysis of a compound can not only tell us what elements are present in a compound, but also exactly how many atoms of each element are in 1 formula unit/molecule. This is represented by a molecular formula.

  3. Kinds of Formulas There is a third kind of formula that shows the arrangementof atoms in the compound. This is called a structural formula. Example: Butyl Alcohol Ethyl Ether -solvent in hairspray -ancient anesthetic Molecular C4H10O C4H10O Empirical C4H10O C4H10O Structural CH3CH2CH2CH2OH CH3CH2OCH2CH3 Expanded

  4. Kinds of Formulas Isomers are ­molecules that have the same molecular formula but a different arrangement of atoms. Butyl AlcoholEthyl Ether Molecular C4H10O C4H10O Structural CH3 (CH2)3OH CH3CH2OCH2CH3 Condensed

  5. Kinds of Formulas Molecular formulas are always whole-numbermultiples of the empirical formula. Example: Hydrogen PeroxideWater Molecular H2O2 H2O Empirical HO H2O Structural HOOH HOH Example: EthyneBenzene Molecular C2H2 C6H6 Empirical CH CH Structural CHCH CHCHCHCHCHCH

  6. A Little O-Chem Anyone? ALCOHOL -OH group bonded to a carbon chain CARBOXYLIC ACID -COOH group bonded to a carbon chain HYDROCARBON only hydrogen and carbon ETHER C-O-C linkage

  7. What holds atoms together in a compound? Atoms combine to form compounds by changing their electron configurations in order to become more stable (*CHEMICAL BONDING*). This is accomplished by either transferring electrons between atoms (ionic bonds) or by atoms sharing electrons (covalent bonds). Covalent bonds are formed when two nonmetals share electrons to form a molecule. A molecule can contain anywhere from two atoms (diatomic molecule) to thousands (biological molecule).

  8. What holds atoms together in a compound? Molecules are made strictly of non-metals. Many molecules make up a molecular(or covalent) compound. A special type of molecule is a diatomicmolecule, which consists of only two atoms. There are only seven elements that exist as diatomic molecules. Incidentally, they make a number seven on the periodic table and begin with atomic number seven.

  9. 7 7 Diatomic Elements

  10. Diatomic Elements ClIFBrOHN(friends with ROY G BIV) • chlorine, iodine, fluorine, bromine oxygen, hydrogen, nitrogen BrINClHOF twins • Anytime you have these seven elements in an uncombined state (not in a compound) they must have a subscript of 2. Example: Br2, Cl2, O2, or H2

  11. Ionic Compounds Metals and nonmetals form ionic compounds by transferring electrons, forming ions, then these ions combine to form a neutral particle. This particle is held together electrostatically by the opposing charges of the cation and anion. A formula unit is the smallest ratio of cations to anions. (Similar to a molecule, actually it is often mistaken for a molecule.) Formula units combine to make an ionic crystal.

  12. Na + Cl2NaCl sodium metal and chlorine gas react to form sodium chloride 2 2

  13. Review An atom of an element is a neutral particle because the number of protons equals the number of electrons. 11p+ 11e- An ion of an element is a charged particle due to the loss or gain of electrons. 9p+ and 10e- This is an atom of sodium. This is an ion of fluorine. It has a –1 net charge.

  14. Review Ions are formed as an element tries to achieve a full valence level of electrons. (Same electron configuration as the nearest noble gas). Except for the first 5 elements, a full valence level is 8 electrons. Eight is great.!!!! In order to achieve these stable configurations, metals always lose electrons, while nonmetals always gain.

  15. Ions Metals form positively charged cations due to the loss of electrons. Ca: 1s22s22p63s23p64s2 The calcium ion will have a configuration of 1s22s22p63s23p6. It has a charge (oxidation number) of +2. Nonmetals form negatively charged anions due to the gain of electrons. O: 1s22s22p4 The oxygen ion will have a configuration of 1s22s22p6. It has a net charge (oxidation number) of –2.

  16. Ionic Charges As a general rule, the resulting charges of ion formation (oxidation numbers) follow a pattern on the periodic table. Metals/Metalloids Nonmetals Alkali metals +1 Alkaline earth metals +2 B Group +3 C Group +4 -4 Pictinogens +5* -3 Chalcogens +6* -2 Halogens +7* -1 Noble Gases 0

  17. Ionic Charges Ions can be divided into two types: monatomic and polyatomic. Monatomic ions consist of ONE ATOM. (mono- means 1). Polyatomic ions consist of MORE THAN ONE ATOM(poly-means many) chemically bonded together and carrying a net charge.

  18. Polyatomic Ions Most polyatomic ions are oxyanions, due to the fact that they consist of oxygen bonded to another element. The names of these ions are a result of the numberof oxygens that are bonded to the central atom. The name has a root taken from the name of the central atom. When an element forms two different oxyanions, the one with the fewer oxygen atoms ends in –ite and the other (more oxygen atoms) ends in -ate .

  19. Polyatomic Ions Table of how to determine various polyatomic ions *per-__-ateone more oxygen, but same overall charge -atetypical polyatomic ion -iteone less oxygen, but same overall net charge *hypo-__-itetwo less oxygen, but same overall net charge. Phosphate *Perchlorate Phosphite Chlorate Chlorite *Hypochlorite *Chlorine, bromine, and iodine can form 4 polyatomic ions that are distinguished by prefixes and suffixes. ClO4-1 PO4-3 ClO3-1 PO3-3 ClO2-1 ClO-1

  20. Sulfate and sulfite oxoanions

  21. OUTER “L”: Those elements that are in the shaded boxes. • In the –ate polyatomic ion, there are THREE (3) oxygens and the charge is 2 LESS than the charge predicted from the periodic table. • The halogen ions ALWAYS have a charge of –1. Polyatomic Ions Continued 6 C 7 N 8 O 9 F 14 Si 15 P 16 S 17 Cl 33 As 34 Se 35 Br 52 Te 53 I IVA VA VIA VIIA • INNER “L”: Those elements in the clear boxes. • In the –ate polyatomic ion, there are FOUR(4) oxygen and the charge is the SAME as predicted from the periodic table.

  22. Polyatomic Ions Continued Cations Ammonium NH41+ Hydronium H3O1+ Mercury (I)Hg22+Mercury (II) Hg2+ Anions AcetateC2H3O21-, CH3CO21-, or CH2COOH1- Azide N31- Benzoate C7H5O22- BorateBO33- ChromateCrO42- CyanateCNO1- CyanideCN1- DichromateCr2O72- FormateHCO21- Hydroxide OH1- Orthosilicate SiO44- Oxalate C2O42- Permanganate MnO41- Peroxide O22- Pyrophosphate P2O74- Tartrate C4H4O62- Tetraborate B4O72- Thiocyanate SCN1- Thiosulfate S2O32-

  23. Polyatomic Ions Polyatomic anions with a charge more negative than -1 may add a hydrogen ion (H+) to give another anion. These anions are named from the parent anion by preceding it with “hydrogen.” These acid anions are oxyanions that are bonded to one or more hydrogen ions. bi- one hydrogen bonded to the polyatomic ion net charge changes by +1. dihydrogen- two hydrogen bond to the polyatomic ion net charge changes by +2. SO4-2sulfate, HSO4-1hydrogen sulfate orbisulfate PO4-3 phosphate HPO4-2hydrogen phosphate orbiphosphate H2PO4-1 dihydrogen phosphate

  24. Formulae / Naming The way a formula is written is dependent on the type of bonding. Formulas for ionic and covalent compounds are written in two different ways. IONIC COMPOUNDS: Because of the large difference in electronegativities in ionic bonding (usually a metal and nonmetal), electrons are transferred between the atoms. This results in the formation of ions. Positive ions called cations and negative ions called anions. These ions are held together by the resulting, opposite electrostatic charges.

  25. Naming Ionic Compounds Therefore when writing formulae for ionic compounds, we use the oxidation numbers (charges) in the CRISS-CROSS METHOD. 1. Write the symbol and oxidation number of each ion in the compound. • If a polyatomic ion is involved, write its formula and oxidation number. • If a transition metal (* or a metal under the staircase*) is involved, its oxidation number is indicated by a roman numeral. Li + F Mg + O Ca + PO4 Cr(III) + Cl Li+1 and F-1 Mg+2 and O-2 Ca+2 and PO4-3 Cr+3 and Cl-1

  26. 2. Now criss-cross by writing the charge on the negative ion as a • subscript for the positive ion, and write the charge on the positive ion as a subscript for the negative ion. • Do not include the (+/-) sign. • If the charges have a common multiple, reduce the charges to their lowest common multiple before completing the criss-cross. • Subscripts of 1 are NEVER written. • 3. If a polyatomic is involved and its subscript is greater than one, then the entire polyatomic ion formula is enclosed in parentheses • and the subscript is written outside of the parentheses.

  27. Li and FMg and OCr(III) and Cl Cr+3 and Cl-1 Mg+2 and O-2 Li+1 and F-1 Mg+1 and O-1 Cr and Cl +3 -1 Li and F +1 -1 Li1F1 Mg1O1 Cr1Cl3 LiF CrCl3 MgO Lithium Fluoride Chromium (III) Chloride Magnesium Oxide

  28. Ca and PO4 Na and CO3 Ca+2 and PO4-3 Na+1and CO3-2 Ca3PO42 Na2CO31 Ca3(PO4)2 Na2(CO3)1 Note: No parentheses are used because the number of polyatomic ions is 1. Ca3(PO4)2 Na2CO3 Sodium Carbonate Calcium Phosphate

  29. Fe(III) and OH Fe+3 and OH-1 Iron (III) Hydroxide Fe1OH3 Note: Parentheses are used and the subscript is written outside the parentheses to show that the entire polyatomic ion is multiplied by the subscript. 3 x OH = 3 O and 3 H atoms Fe1(OH)3 Fe(OH)3

  30. Naming Ionic Compounds : Nomenclature Ionic compounds are mainly composed of metals bonded to nonmetals. To name these structures you must first recognize what elements are in the compound and their locations on the periodic table. • If the compound consists of a metal with only has 1 oxidation number (i.e. NOT A TRANSITION METAL or A METAL BELOW THE STAIRCASE): • Write the name of the metal. • Add the name of the negative element, modified to end in -ide. DO NOT CHANGE THE NAME OF A POLYATOMIC ION. Al2S3 CaCO3 Aluminum Sulfide Calcium Carbonate

  31. Naming Ionic Compounds : Nomenclature • If the compound consists of a transition metal or a metal under the staircase. • Write the name of the metal. • After the name, indicate its oxidation number by a Roman Numeral. EXCEPTIONS: Silver is always a +1 Zinc is always a +2 Cadmium is always a +2 Aluminum is always a +3

  32. Naming Ionic Compounds : Nomenclature *To find the oxidation number of the transition metal, you must first look at the oxidation number of the non-metal and use it to solve for the transition metal. Examples: FeO 1 Fe+x and 1 O-2 Fe2O3 2 Fe+x and3 O-2 1 Cu+xand1C2O4-2 CuC2O4 x +(-2) = 0  x = 2 2x + 3(-2) = 0 2x = 6 x = 3 x +(-2) = 0  x = 2 Iron (II) Oxide Copper (II) Oxalate Iron (III) Oxide

  33. Naming Systems There are many systems of naming compounds that date back for many years. Unfortunately, all three systems are used today so it is important to understand and use all three systems. The three systems are: Stock system Classical system Informal system

  34. Naming Systems Thus far you have been using the stock system, which involves using Roman numerals to indicate the charge of the transition metal cation. In an older system of nomenclature, such ions are named by adding the suffixes –ic and –ous to a stem of the latin name of the element. The –ic ending corresponds to the highercharge while the -ous ending denotes the lower charge. YOU CAN EASILY REMEMBER THIS NAMING RELATIONSHIP BECAUSE THERE IS AN “O” IN “OUS” AND “LOW,” AND AN “I” IN “IC” AND “HIGH.”

  35. Formulae for Molecular Compounds Order of elements in the formula: • Except for hydrogen, the element farther to the left in the periodic table appears first: SiO2, PCl3 • If hydrogen is present, it appears last except when the other element is from column VIA or VIIA of the periodic table: NH3, CH4, H2S, HCl • If both elements are from the same column of the periodic table, the lower one appears first: SiC, BrF3 • The element that appears first retains its elemental name.

  36. Formulae for Molecular Compounds (con’t) 5. The second element bears a root derived from its elemental name and ends with the suffix –ide Common RootsBr  Bromo­Cl  Chlor­C   Carb­F   Fluor­H   Hydr­

  37. Formulae for Molecular Compounds (con’t) 6.When there is more than one atom of a given element in the formula, the name of the element usuallycontains a prefix that specifies the number of atoms present. Common Prefixes: Number Prefix 1 mon(o) 2 di 3 tri 4 tetr(a) 5 pent(a) 6 hex(a) 7 hept(a) 8 oct(a) 9 non(a) 10 dec(a) Note: If the numerical prefix ends with the letter o or a and the name of the element begins with a vowel, the last letter of the prefix is dropped.

  38. Formulae for Molecular Compounds (con’t) If the first element has only one atom, do not use a prefix. CO CO2 N2O5 CCl4 Do Not use MONO- here ___carbon monoxide ___carbon dioxide dinitrogen pentoxide ___carbon tetrachloride

  39. Stock Names for Molecular Compounds • The names of these compounds can also be written using the stock system. • In order to do this you must remember a few rules. • Fluorine is always a –1. • Cl, Br, and I are always a –1, unless bonded to F. • H is +1 and O is –2 in most compounds. • The algebraic sum of the oxidation numbers in a neutral compound is zero; (in a polyatomic ion, the sum must equal the ion charge.) • CO • CO2 • N2O5 • CCl4 Carbon (II) oxide Carbon (IV) oxide Nitrogen (V) oxide Carbon (IV) chloride

  40. Formulae for Molecular Compounds (con’t) ammonia. The following is a list of compounds that use an informal naming system. NH3 is not nitrogen trihydride, it is CH4 is PH3 is called AsH3 is called NO is N2O is H2O is NOTE: The formulas of carbon containing compounds start with carbon, followed by hydrogen. After that, any other elements appear in alphabetical order. Examples: C2H6O, C4H9BrO, CH3Cl methane. phosphine. arsine. nitric oxide. nitrous oxide (laughing gas) water.

  41. Acids All acids contain hydrogen, and their formulas begin with “H.” Note: A hydrogen compound that is dissolved in water is an acid. If it is notdissolved in water name it according to the criss-cross method. • There are two types of acids. Ones that contain oxygen and ones that do not. • Acids that contain oxygen in their formula are termed oxyacids. • Oxyacids are made when hydrogen bonds to an oxyanion. The formulas are written as if H+1, following the criss-cross method.

  42. Oxyacids Oxyacids are named according to the polyatomic ion. Change –ate to –ic acid “O, I ate too much, I feel icky!” Hydrogen and acetate ion Hydrogen and carbonate ion hydrogen acetate as a gas H+1 (+) C2H3O2-1 HC2H3O2 Acetic acid as an aqueous solution hydrogen carbonate as a gas H+1 (+) CO3-2 H2CO3 Carbonic acid as an aqueous solution

  43. Oxyacids (con’t) Change –iteto –ous acid. At nite, we rob houses! Hydrogen and nitrite ion H+1 (+) NO2-1 Hydrogen and sulfite ion H+1 (+) SO3-2 hydrogen nitrite as a gas HNO2 Nitrous acid as an aqueous solution hydrogen sulfite as a gas H2SO3 Sulfurous acid as an aqueous solution

  44. If you do acids, you may suffer from a condition called ATE-IC-ITE-OUS

  45. Diagram illustrating how to name oxoacids

  46. Acids If there is nooxygen in the formula, then the acid is named with the prefix hydro- then the root and the -ic suffix. HBr(g) is HBr(aq) is HCl(g) is HCl(aq) is H2S(g) is H2S(aq) is HCN(g) is HCN(aq) is hydrobromic acid hydrogen bromide hydrochloric acid hydrogen chloride hydrosulfuric acid hydrogen sulfide hydrogen cyanide hydrocyanic acid

  47. Illustration of a binary compoundand its corresponding acid solution

  48. Hydrates Hydrates: compound that contains water molecules weakly bonded in its crystal structure. • These are obtained by evaporatingan aqueous solution of a compound. • They are named according to the anhydrouscrystal followed by a prefix indicating the number of water molecules per formula unit, and finally the word hydrate, which means water. • These are the same prefixes used to name binary molecular compounds. CuSO4. 5 H2O is CoCl2. 6 H2O is copper (II) sulfate pentahydrate. cobalt (II) chloride hexahydrate.

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