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Naming Compounds. What's in a name? That which we call a rose By any other name would smell as sweet." - William Shakespeare, Romeo and Juliet (II, ii). BACKGROUND:.
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Naming Compounds What's in a name? That which we call a roseBy any other name would smell as sweet." - William Shakespeare, Romeo and Juliet (II, ii)
BACKGROUND: Prior to the 1700s, there was no systematic method of naming compounds. Substances were named in variety of ways, such as the use of compounds, the property of the compound, or the source of the substance. These names give little, if any, information about the composition of the compound.
Common Name: Quick lime/ Lime IUPAC Name: Calcium Oxide Chemical Formula: CaO Use or property: Neutralizing acidified lakes
Common Name: Baking Soda IUPAC Name: Sodium bicarbonate Chemical Formula: NaHCO3 Use or property: Making baked goods rise
Common Name: Laughing gas IUPAC Name: Dinitrogen monoxide Chemical Formula: N2O Use or property: Used in dentistry as anaesthetic
Common Name: Table salt IUPAC Name: Sodium Chloride Chemical Formula: NaCl Use or property: Enhancing flavour
Common Name: Quartz sand IUPAC Name: Silicon dioxide Chemical Formula: SiO2 Use or property: manufacturing glass
Background: valences and formulas • Valence electrons are the number of electrons in the outer energy level of an atom. • “Valence” describes the number of electrons gained, lost or shared to achieve stability. • For first 20 elements valence starts at 1 (alkali metals), climbs to 4 (group 4) and falls back to 1 (halogens) • By knowing the valence of elements you can determine the formula of compounds • E.g. what compound would form from C + S? Step 1 - write valences: Step 2 – balance valences by adding atoms: Step 3 – write # of each atom as a subscript C S 4 2 • C S • 2 • 2 CS2
a) Al,Br b) K,S c) Zn,O d) Mg,N e) C,Cl f) Na,O • Al Br • 1 • 1 • 1 • AlBr3 K S 1 2 1 K2S Zn O 2 2 ZnO Mg N 2 3 2 3 2 Mg3N2 C Cl 4 1 1 1 1 CCl4 Na O 1 2 1 Na2O Na2O AlBr3 K2S ZnO Mg3N2 CCl4
Ionic compounds Rules for naming • Names end in -ide. Example: sodium chloride • 1. Write metal name first then non metal • 2. Change the ending of the non metal to “ide” • 3. Do not capitalized unless starting a sentence Give formulae & name: Ca + I, O + Mg, Na + S = Ca2I1 = CaI2 = calcium iodide = Mg2O2 = MgO = magnesium oxide = Na1S2 = Na2S = sodium sulfide
Multiple Valence • Some metals have more than one valence. • For these metals, you can use the Latin or IUPAC method • Latin is older (not useful for some compounds) • IUPAC is more commonly used
Latin naming • As before, the metal name if written first and the non metal ends in -ide • The metal is named with it’s Latin or English root and ends in “–ic” or “–ous” to denote valence • E.g. Cu1 is cuprous, E.g. Cu2 is cupric • Lower = ous, Higher = ic • Give formulas and Latin names for: Cu2 + Cl = Cu2Cl1 = CuCl2 = cupric chloride Cu1 + Cl = Cu1Cl1 = CuCl = cuprous chloride
FeCl2 Fe -> +2 Cl -> -1 CuO Cu -> +2 O -> -2 Name the following: • Ferrous chloride - Cupric oxide
IUPAC naming • Metal comes first, ending of non metal is “ide” • The valence of the metal is indicated in brackets using roman numerals • E.g. Cu1 is copper(I), Cu2 is copper(II) • Numbers refer to valences not to #s of atoms • Try: Cu2+Cl, Zn2 + Cl, Co2+Cl, Hg+S (do both) Cu2+Cl = Cu2Cl1 = CuCl2 = copper(II) chloride Zn2+Cl = Zn2Cl1 = ZnCl2 = zinc chloride Co2+Cl = Co2Cl1 = CoCl2 = cobalt(II) chloride Hg+S = Hg1S2 = Hg2S = mercury(I) sulfide Hg+S = Hg2S2 = HgS = mercury(II) sulfide
So far we have given valences to single atoms Li + O Compounds containing polyatomic ions Li1O2 Li2O • Groups of atoms can also have valences • “Polyatomic ions” are groups of atoms that interact as a single unit. • E.g.OH1,(SO4)2. Ba3(PO4)2 = barium phosphate • Naming compounds with polyatomic ions is similar to naming other ionic compounds • Put the metal name first, then the name of the polyatomic second. • You should note that compounds with polyatomic ions have names ending in -ate or -ite not -ide • Name: Ca(OH)2, CuSO4, NH4NO3, Co2(CO3)3
Compounds containing polyatomic ions Ca(OH)2 CuSO4 NH4NO3 Co2(CO3)3 - calcium hydroxide - copper(II) sulfate - ammonium nitrate - cobalt(III) carbonate
Naming covalent compounds • prefixrefersto#ofatoms-notvalence • N2O4 = dinitrogen tetroxide • Exception:dropmonoforfirstelement • CO2 = carbon dioxide • The first vowel is often dropped to avoid the combination of “ao” or “oo”. • CO=carbonmonoxide(monooxide) • -ide ending, each element has “prefix” P4O10= tetraphosphorus decoxide SO2= sulfur dioxide (doxide) • Name: CCl4, P2O3,IF7
Write and name the following covalent compounds (IUPAC) carbon tetrachloride diphosporus trioxide iodine heptafluoride CCl4 P2O3 IF7
Write the formulas for the following covalent compounds (IUPAC) dicarbon tetrasulfide pentaphosphous dioxide iodine octafluoride C2Cl4 P5O2 IF8