Naming Compounds - Chemistry Lecture Notes PDF

CHAPTER 4 NAMING COMPOUNDS What is Chemical Bonds A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds  IONIC BONDS  Electrons are transferred  Electronegativity differences are genera...

CHAPTER 4 NAMING COMPOUNDS What is Chemical Bonds A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds  IONIC BONDS  Electrons are transferred  Electronegativity differences are generally greater than 1.7  Ionic substances are formed when an atom that loses electrons relatively easily react with an atom that has a high affinity for electrons.  are formed by the attraction of oppositely charged ions.  The formation of ionic bonds is always exothermic Covalent bonds Often found between two nonmetals. Typical of molecular species. Atoms bonded together to form molecules. Strong attraction. Atoms share pairs of electrons to attain octets. Molecules generally weakly attracted to each other.  Metallic bonds Metallic bonds are the forces of attraction between free-floating valance electrons and positively charged metal cations. In metal, cations are packed closely together The loosely held held valence electrons of the metal atoms form a sea of electrons that drift freely from one part of the metal to another The overall charge of metal is neutral  problems for electronegativi ty Predict which of the following compounds are ionic and which are covalent, based on the location of their constituent atoms in the periodic table: a. Cl2CO b. MnO c. NCl3 d. CoBr2 e. K2S DIFFERENT TYPES OF CHEMICAL BONDS CHEMICAL FORMULAS shows the kind and numbers of atoms in the smallest representative unit of the substance.  Nomenclature Rules What type of compound is it? IONIC COMPOUND: COVALENT COMPOUND: ACID: Composed of cations (metals Nonionic – not composed of cations Produces H+ in water. or polyatomic ions) and anions & anions. Typically the hydrogen cation (nonmetals or polyatomic Generally, only nonmetals are is written first in the ions). present. chemical formula. TYPE I: TYPE II: TYPE III: ACIDS: OXYACIDS: Only one type More than one Covalent, Anion does not Anion does of cation is type of cation is nonionic. contain oxygen. contain oxygen. observed. observed. Chemical reactions occur when atoms gain, lose, or share electrons. Metals Nonmetals Nonmetals gain / _____________ accept electrons. _ This gives themanions a ____ Metals charge. lose ________________ / Negative + called ions are electrons. donate ___________. This gives themcations a ____ Remember that the charge of an ion can be determined by its place on the Periodic Table. + + 0 1 4 + + or -3 -2 -1 2 3 -4 Look for the Roman Numeral! Formula writing A simplified method of writing formulas of ionic compounds is the crisscross method. The following 1.rules are helpful. The symbol of the positive ion is written 1st followed by the negative ion. 2. If the subscript is 1 it is not written 3. Criss – cross i.e, the valance of the positive ion becomes the subscript of the negative ion, while the valence of the negative ion becomes the subscript of the positive ion. 4. If the valance are numerically equal, there is no need to criss- cross since the sum of the valences is zero 5. If the subscript of the radical is greater than 1 the radical is enclosed with parenthesis 6. Subscript should be reduced to the lowest How to name ionic compounds RULE 1 ; BINARY COMPOUNDS MUST CONTAIN METAL AND NON-METAL CaB m r calciu bromid 2 e Step 1: Write the name of the metal Step 2:ion. Write the name of the nonmetal ion.add –ide to the Non- Step 3: Then Metal Exercise Name the following: NaF MgO Strontium chloride Lithium sulphide NaCl MgI2 Rules for naming polyatomic ions Rule the name of the positive ion is given first followed by name of the negative radical which either end in ite or ate - -ite is used when the middle ion uses lower oxidation - - ate is used the higher oxidation umber is used This is just as easy to do with polyatomic ions. You just need to use the name of the polyatomic ion. strontium nitrate Sr +2 NO- Sr(NO 33 metal Step 2:ion. ) Step 1: Write the symbol of the 2 Write the formula of the polyatomic ion. Step 3: Determine the charges using the periodic table and the table of Step 4: Determine polyatomic ions. the formula from the ions. There are also ions that form after elements have shared electrons. These ions are known as polyatomic ions, and each polyatomic ion already has a name. When polyatomic ions are used, simply use the name of the polyatomic ion in th compound. NH F 4 ammonium fluoride Mg(NO3)2 magnesium nitrate How to name TYPE II Compound  Remember that the names of transition metals include their charge because their charges are less predictable. What are the charges of the transition metals below: Iron (II)+ _______ Iron (III)+ _______ 2 + 3+ Copper + (II)2 _______ + 1 (I) Copper _______ 4 + 2+ TinWe(IV) _______ 2 know Tin (II) 4 they are positive _______ because metals are always Lead (II) _______ Lead (IV) positive. The charges of the transition metals are important when you are determining the formula of an iron ionic (III) compound. oxide Fe+3 O-2 Fe2O3 Step 1: Write the symbol of the cation. Step 2: Write the symbol of the anion. Step 3: Determine the charges using the periodic table and the roman numerals. Step 4: Determine the formula from the ions. How to name TYPE II Compound Using Traditional names Use a roman numeral after atoms whose valance the cation to indicate the numbers vary ionic charge of that cation add the suffix –ous to the FeO would be called iron(II) oxide since the one with the lower cation is valence state would be called iron(III) add the suffix –ic to the oxide since the cation is one with the lower valence state FeO would be called Ferrous Oxide since the cation is Write the formula of each of the ionic compounds named KI SnCl 4BaS O NaCl 4 SrS CuCO 3AlBr Li33N Naming of covalent compounds For covalent containing 2 non-metals Steps: 1. Name the electropositive 1st 2. Write the name of the 2nd element with –ide ending 3. Use prefixes to tell the number of atoms of each element Note: Mono is never used to name the First element Naming acids and oxy-acids NAMING BINARY ACIDS: The name of the binary acid consists of two words. The first word has three parts: The second word is always the “hydro” prefix “acid” the root of the nonmetal element the “ic” ending Examples: HCl = hydro chlor- ic acid = hydrochloric acid HBr = hydro brom -ic acid = hydrobromic acid HF = hydro fluor ic acid = hydrofluoric acid NAMING OXYACIDS: These are more difficult to name because these acids have hydrogen, a nonmetal, and may have varying numbers of oxygen atoms. For example, H2SO5, H2SO4, H2SO3, and H2SO2 are all acids Once we have our point of reference the acid with one more oxygen than the -ic acid is called the per-_________-ic acid. The acid with one less oxygen then the -ic acid is called the ___________-ous acid. If the acid has one less oxygen than the -ous acid, it is called the hypo- ____________-ous acid.