Chemical Nomenclature (Modern Chemistry Ch. 7)

Transcription

1 Chemical Nomenclature (Modern Chemistry Ch. 7) The System The governing body responsible for chemical nomenclature is the International Union of Pure and Applied Chemistry (IUPAC). There are two major division to the IUPAC system... The System 1. Organic nomenclature contain carbon, usually bonded with hydrogen, oxygen, nitrogen, and sulfur. This is a college course. 2. Inorganic nomenclature everything else is inorganic and is divided into three categories... Covalent (aka molecular) compounds Ionic compounds Acids Element Categories on the Periodic Table To name and write formulas for chemical compounds, you must be able to classify elements first. Metalloids: B, Si, Ge, As, Sb, Te, Po (PURPLE) Nonmetals: elements to the right of the metalloids, and hydrogen (GREEN) Metals: everything YELLOW This unit covers inorganic nomenclature

2 Groups on the Periodic Table We will often refer to GROUPS (columns) by name. We do this because elements in groups (a.k.a. families) behave similarly. Group 1 Alkali Metals (**hydrogen is not a metal!) Group 2 Alkaline Earth Metals Group 13 The Boron Group Group 14 The Carbon Group Group 15 The Nitrogen Group Pnictogens, rarely Group 16 The Oxygen Group Chalcogens, rarely Group 17 The Halogen Group Group 18 The Noble Gases Naming Elements Most elements exist as parts of molecules (covalent compounds) or ionic compounds. Only noble gases truly exist in their elemental, monoatomic, form in nature. 1. Naming Monoatomic Elements just as they appear on the periodic table. (ex. Na is sodium, P is fluorine) 2. Naming Diatomic Elements same. There are seven. Hydrogen,Oxygen, Bromine, Iodine, Fluorine, Chlorine, Nitrogen (ex. H 2 is hydrogen) Naming Ions Monoatomic ions are atoms that have lost or gained electrons. 1. Cations usually metals, electrons have been lost. Name by writing the "element name + ion". K + is potassium ion. 2. Anions usually nonmetals, electrons have been gained. Element suffix changed to "ide". S 2 is sulfide Polyatomic Ions 2 or more atoms bound in a covalent (defined soon!) bonds with a charge. You will memorize these. Oxidation State the degree to which an atom is oxidized (electrons take away) > in an unbound element (Na, Cl 2 ) is zero > in a monatomic, monovalent ion, is equal to the net charge on the ion. > the sum of oxidation states of the atoms in a compound is zero > the sum of oxidation states of the atoms in an ion is = to the charge on the ion!

3 Nomenclature Pre AP Chemistry Ion Breakdown Multivalent Ions and 3 To Know... Lost or gained e? How many? Ion formed Sodium Na+ Chlorine Cl Memorize the charges for these 3 ions: Oxygen O2 Ag is 1+ Zn is 2+ Cd is 2+ Aluminum Metal or nonmetal? If an atom has no consistent charge, meaning it loses or gains a variable amount of electrons in reactions, it is said to be multivalent. Element Name Elements in Groups 3 12 and 14 are multivalent. Three atoms in these groups DO form monovalent cations, they are silver (+1), zinc (+2), and cadmium (+2). 3+ Al Classifying Compounds Classifying Compounds Ternary compounds consist of three different elements. Ionic compounds are composed of a cation (written first) and an anion (second) joined by strong electrostatic forces. Either ion may also be replaced w ith a polyatomic ion. Form 3D crystal lattices. Ex: Na2SO4, NH4Cl, C6H12O6 Examples: NaCl, Al2(SO3)3 Binary compounds consist of two different elements. Ex: NaCl, SCl6, Al2O3 Quaternary compounds consist of four different elements. Ex: (NH4)3PO3

4 Nomenclature Pre AP Chemistry Classifying Compounds Classifying Compounds Molecular (covalent) compounds are composed of nonmetal atoms joined by covalent bonds. The combined attraction of the atomic nuclei for each others' electrons attracts the atoms to each other in this "shared" bond. Metalloids may also be present in molecular compounds. Acids are composed of a hydrogen ion (or ions!) covalently bonded to either a monoatomic anion or a polyatomic anion. Examples: HF, H2S, HClO3, H2SO4 Examples: O2, H2O, AsCl3, C12H22O11, P4O10 Classifying Compounds Why Bonds Form. Bases are ionic compounds composed of a cation and hydroxide (OH ). One exception is ammonia (NH3). When bubbled through water, ammonia, a gas, forms ammonium hydroxide. Most elements are not stable in their elemental state. Think about the noble gases. Atoms are most stable when the valence shell is full of electrons (we will explain why soon enough). Examples: NaOH, NH4OH, Ca(OH)2 Strong electrostatic (difference in charge) forces attract oppositely charged ions in ionic bonds. Electron attraction to a nearby nucleus creates covalent bonding. Once forces of attraction are sated, the new compound has no charge!

5 Why IONIC Bonds Form Strongly electronegative nonmetals are able to take electrons from less attractice metal atoms. This gives both atoms charge, which makes them ions. Oppositely charged ions attract (electrostatic attraction) in whole number ratios and tend to form crystals. Hence, IONIC bonding. Binary Ionic Compounds A single cation binds to a single anion (there can be more than one of each!). Binary of two parts. Ba 2+ I 1 Ba 1 I 2 BaI 2 Ba 2+ I 1 Ba 1 I 2 BaI 2 Writing Formulas for Binary Ionic Compounds Writing Formulas for Binary Ionic Compounds STEP #1 1) Determine the charge (oxidation number) on each ion ~ These are monovalent ions The trend for that ion's group is the charge. STEP #2 2) Write the cat ion with charge first, and the anion with charge second. (same order as in the written name) magnesium fluoride Ionic compound formulas are written cationfollowed by the anion. Ionic compound formulas are written cationfollowed by the anion.

6 Writing Formulas for Binary Ionic Compounds STEP #3 3) Manipulate quantities of cation and anion as subscripts to balance charges. The total compound charge should equal zero. Cation and anion should be in lowest whole number ratio. Mg 2+ F 1 magnesium fluoride Ionic compound formulas are written cationfollowed by the anion. Writing Formulas for Binary Ionic Compounds Write formulas for the following ionic compounds Name of compound Cation Anion Formula of compound Barium iodide Ba 2+ I - BaI 2 Calcium oxide Magnesium chloride Sodium nitride Naming Binary Ionic Compoun Naming Binary Ionic Compoun RULES To name any ionic compound, simply name the cation and anion in order. Boom done. Name the following: 1. LiCl lithium chloride 2. CaF 2 3. Ra 3 N 2 4. Na 2 O Ionic compound formulas are written cationfollowed by the anion.

7 Writing Formulas for Ionic Compounds with Polyatomic Ions Writing Formulas for Ionic Compounds with Polyatomic Ions Polyatomic ions can act as: cations (ammonium, that's pretty much the only one), and anions (the rest). You have memorized them. BE CAREFUL, "ite" is NOT "ide"! RULES: Write the cation and anion. Balance charges. Place parentheses around P.I. if you need more than one. DO NOT alter the formula of the P.I. EVER. DO NOT "distribute" numbers into parentheses. Example: ammonium carbonate These are ternary compounds unless ammonium is the cation, which can make them quaternary. Example: aluminum nitrate Writing Formulas for Ionic Compounds with Polyatomic Ions Naming Ionic Compound with Polyatomic Ions Write formulas for the following ionic compounds Name of compound Cation Anion Formula of compound Calcium chlorite Ca 2+ ClO 2 1 RULES Write each ion's name. DO NOT change a polyatomic ion's name OR formula. Example: Ca 3 (PO 4 ) 2 Magnesium bisulfate Gallium dichromate

8 Naming Ionic Compound with Polyatomic Ions Practice By Building Build the compound by dragging the ions together until charges add up to 0. Write the formula. Calcium phosphate Name the following 1. LiCN lithium cyanide 2. Sr 3 (PO 3 ) 2 Pull 3. Zn(OH) 2 4. (NH 4 ) 3 BO 3 calcium ion (Ca 2+ ) nitrate (NO3 ) aluminum ion (Al 3+ phosphate (PO4 3 ) ) hydroxide (OH ) Al Ca N 1 O O O O H O O P O 3 O Writing Formulas of Ionic Compounds with Multivalent Cations Writing Formulas of Ionic Compounds with Multivalent Cations Many cations are multivalent. Most transition metals have several oxidation states. Manganese has 7!!! When written, the oxidation state is given in Roman numerals following the cation, in parenthesis. This is called the "stock" system. Example: Copper can be copper (I) or copper (II). RULES: 1. Write each ion. Remember, the CATION charge is in parentheses! 2. Balance charges. Rules for P.I.'s still apply. Example: lead (II) oxide copper (I) chloride Cu 1+ CuCl Example: tin (IV) sulfide copper (II) sulfate Cu 2+ CuSO 4 I II III IV V VI VII VIII I II III IV V VI VII VIII

9 Nomenclature Pre AP Chemistry Writing Formulas of Ionic Compounds with Multivalent Cations Naming Ionic Compounds with Multivalent Cations Write formulas for the following ionic compounds Cation Name of compound Iron (III) iodide Fe 3+ Anion Formula of compound FeI3 I RULES Write each ion. Determine the charge of the multivalent cation You will work backward from the formula to find the charge! Write the charge as a Roman Numeral in parenthesis after the cation Rules for P.I.'s still apply. Example: CoCl2 Lead (II) nitrate Manganese (VII) oxide I II III IV V VI VII VIII I II III IV V VI VII VIII Naming Ionic Compounds with Multivalent Cations tin (II) carbonate 1. SnCO3 2. SnF4 3. Ti(NO3 ) 4 Writing Formulas for Hydrates Hydrates are ionic compounds that contain water molecules in the crystal. Most IONIC compounds hydrate naturally due to water's attractiveness to charge, prevalence, and available binding locations in the crystal. The water is not part of the chemical substance and this is reflected in the way the formula is written (below). When no water is bound to an ionic crystal, it is said to be anhydrous. 4. FePO4 I II III IV V VI VII VIII CuCl2 anhydrous They look different but behave the same when dissolved in water. CuCl2 2H2O

10 Writing Formulas for Hydrates Here is an example: CoC 2 O 4 2H 2 O. Look at the crystal below. Water molecules are bound at specific intervals in the crystal. This changes the physical properties of the crystal, but no chemical difference is made. Formula CoC 2 O 4 2H 2 O Name cobalt (II) oxalate dihydrate The dot does NOT mean multiply! Writing Formulas for Hydrates RULES: Use the ionic naming rules. Follow the chemical formula by adding a dot and the hydrate preceded by the prefix number in the below table. MEMORIZE the table below. These are the prefixes that represent the number of water molecules per ionic formula unit. Example: sodium nitrite trihydrate Writing Formulas for Hydrates Write formulas for the following ionic compounds Name of compound Formula of compound gold (III) chloride tetrahydrate calcium carbonate dihydrate AuCl 3 4H 2 O Naming Hydrates RULES: Use normal ionic naming rules. Name the hydrate Use the prefixes below attached to "hydrate" Example: MgSO 4 7H 2 O zinc sulfate monohydrate aluminum perchlorate nonahydrate

11 Naming Hydrates Writing Formulas for Binary Molecular Compounds Name the following 1. SnCl 4 5H 2 O tin (IV) chloride pentahydrate 2. GaF 3 3H 2 O 3. Ni(C 2 H 3 O 2 ) 2 4H 2 O RULES 1. Write the symbol for the first term. 2. Add the subscript that corresponds to the number of atoms present in the compound. See prefix chart below. 3. If no prefix is written, assume one atom of that element is in the formula the prefix MONO is not used in the first term of a molecular compound 4. Write the symbol for the second term. 5. Add the subscript that corresponds to the number of atoms present in the compound. See prefix chart below. Writing Formulas for Binary Molecular Compounds Write formulas for the following: 1. nitrogen dioxide 2. carbon monoxide 3. phosphorus pentachloride Naming Binary Molecular Compoun RULES 1. Name the first term 2. Include a prefix if two or more atoms of that element are present Never use the prefix MONO for the first term. 3. Name the second term and change the ending to ide, much like you would an anion. 4. Include a prefix in all cases to show the number of atoms.

12 Name the following: Naming Binary Molecular Compoun Molecular Compounds with Common Names 1. PCl 3 2. OF 2 3. SiO 2 A few common compounds have common names that are used instead of their molecular names. Always use the common name! CH 4 NH 3 H 2 O Methane not carbon tetrahydride Ammonia not nitrogen trihydride Water not dihydrogen monoxide Naming Acids There are two ways acids are named depending on their construct. 1. Binary acids consist of a hydrogen ion (H+) and an anion that doesn't contain oxygen. (HCl, HCN) 2. Oxoacids are hydrogen ion and a polyatomic anion containing oxygen. Oxoacids are often ternary. (H 2 SO 4, HClO) Naming Acids To name a binary acid... Start with hydrodetermine the root of the anion followed by "ic" then add "acid". Examples: HCl Cl is the anion, its name is chloride Name of acid is: HF F is the anion, its name is fluoride Name of acid is:

13 Naming Acids To name a oxoacid... Name the polyatomic ion. If it ends in "ATE": Change end of polyatomic ion to "IC" and add "acid" Examples: HNO 3 NO 3 1 is the anion, its name is nitrate Name of acid is: H 2 CO 3 CO 3 2 is the anion, its name is carbonate Name of acid is: Naming Acids To name a oxoacid... Name the polyatomic ion. If it ends in "ITE": Change end of polyatomic ion to "OUS" and add "acid" Examples: HNO 2 NO 2 1 is the anion, its name is nitrite Name of acid is: HClO 2 ClO 2 1 is the anion, its name is chlorite Name of acid is: I ATE something ICky The snake bite was poisonous A Special Note About Sulfur and Phosphorus As you know... The ions for sulfur and phosphorus are sulfide and phosphide. ALAS... When the anion of an acid contains sulfur or phosphorus, the roots are sulfur and phosphor, respectively, not sulf and phosph. So... H 2 SO 4 is sulfuric acid, not sulfic acid H 3 PO 4 is phosphoric acid, not phosphic acid. RULES 1. Determine the anion 2. Hydrogen ion (H + ) binds the anion 3. Balance charges with subscripts Examples: Writing Formulas for Acid Hydrobromic acid anion is bromide (Br ) formula is Acetic acid anion is acetate (C 2 H 3 O 2 ) formula is Phosphorous acid anion is phosphite (PO 3 3 ) formula is Sometimes life isn't fair. Please accept my apologies on behalf of the well meaning people at IUPAC.

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