UNIT 8: CHEMICAL FORMULAS AND NOMENCLATURE CHEMISTRY 215, DUFFEY

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1 UNIT 8: CHEMICAL FORMULAS AND NOMENCLATURE CHEMISTRY 215, DUFFEY BIG IDEAS o 7.1 Ion formation - o 7.2 Ionic bonding - o 7.4 Metallic bonding - o 8.1 & 8.2 Covalent bonding - CHEMICAL BONDING o The purpose of bonding in any form is to Which elements on the periodic table are already stable? Why? o Any atom with a is stable, it is to be more stable. Atoms generally achieve this by (ionic) or (covalent) electrons CHEMICAL FORMULAS o A chemists shorthand way of indicating Shows which elements are Subscripts indicate the relative or actual number of unit or molecule o Formula Unit ( ) Repeat to form a o Molecule ( ) Exist as, no of each element in a formula O = C = O IONIC BONDS o Transfer of from cation to anion The oppositely charged electrons have an (+/-) that forms the bond. o Ionic compounds are formed. Binary Ionic Compounds Contain only two different Generally form between a Other Ionic Compounds Contain more than A metal or nonmetal with a (or polyatomics) between them

2 Duffey, Chem 215, Unit 8 Notes, p. 2 IONIC COMPOUND FORMATION o Formation occurs in a way that the compound is (carries no overall ) Example a compound formed from and To form a compound that is you need: o Ca 2+ for every F 1- [ ] So the formula for the neutral compound is The simplest method for this is to Example - and o Take the from the Cu and give it to as a o Take the from the S and give it to as a FORMULA: (then reduce if needed) EMPIRICAL FORMULAS o Ionic compounds consist of so they ONLY have empirical formulas Empirical Formula a chemical formula that shows the rather than the actual number of atoms in the substance This means that two different empirical formula since it is not the Example o Ethyne is o Benzene is WRITING FORMULAS FROM NAMES o Polyatomic Ions compounds can have the formula for the substance empirical formula empirical formula If you need more than one of a polyatomic ion you will need to use Example: Aluminum Carbonate BE ESPECIALLY CAREFUL WITH THESE IONS: THESE ARE THE MOST COMMON MISTAKES MADE WITH FORGETTING PARENTHESIS!!! o Empirical Formulas See the Writing Formulas From Names Reference sheet o Ionic Formula Writing Examples: YOU TRY Write ionic formulas for: Lithium Chloride Sodium Fluoride Calcium Bromide Nickel (II) Acetate Magnesium Phosphate Calcium Cyanide Ammonium Carbonate Potassium Sulfite Copper (II) Hydroxide Mercury (I) Bromide Barium Sulfate Manganese (II) Sulfide Zinc Nitrate Magnesium Bisulfate

3 PROPERTIES OF IONIC COMPOUNDS o Ions are packed in a regular and repulsion between the ions. Duffey, Chem 215, Unit 8 Notes, p. 3 that balances the forces of attraction o Electrical Conductivity Ionic compounds conduct as solids, but do if they are or Conductivity depends on available o An ionic compound whose solution ( called an o A compound whose solution does conduct is a o High Melting Point/High Boiling Point Due to relatively ) conducts is Lattice Energy is the energy required to the solid compound into o Crystals with Transition Metals are often The colors are also seen when they are in o Ionic Crystals are hard, rigid, and brittle as They can be METALLIC BONDS o Metals can form bonds with the same principles as Lattices are based on o Sea of Electrons Metals in the lattice do not,, or their electrons Instead the overlap to form a The outer electrons are then by an specific atom and can move easily between This is called Metallic bond: o PROPERTIES OF METALS Melting and boiling points vary greatly In general they have Malleability, Ductility, and Durability, can be drawn into a or hammered into a Thermal and Electrical Conductivity (electrons are already moving around) Hardness and Strength Transition metals actually use some of their and create stronger bonds due to more electrons. Alkali metals have delocalized e -, so they are

4 o Metal Alloys It is relatively to introduce other elements into Alloy a mixture of elements that has a o Duffey, Chem 215, Unit 8 Notes, p. 4 Properties of Alloys o from the elements they contain o Specific combinations are used to achieve the Added elements like also contribute COVALENT BONDS o Form by the Generally form between A is formed The shared electrons are considered to be part of the o Example: Diatomic Molecules F 2 H 2 N 2 Br 2 O 2 Cl 2 I 2 Memory Trick o COVALENT BOND FORMULA WRITING See the Writing Formulas From Names Reference sheet o Covalent Formula Practice: Sulfur dioxide Dinitrogen trioxide Diphosphorus pentoxide Tetracarbon decahydride Nitrogen monoxide o Molecular Formulas (in general) Represent compounds that exist in (covalent only!) Subscripts tell the of elements/atoms Subscripts show a simple whole number ratio o Then the molecular formula is the same as the Or the ratio between subscripts may be of the empirical ratio Examples: Empirical formula: H 2 O CO 2 CH 4 C 2 H 6 C 4 H 10 o Multiple Bonds Bond strength is dependent on bond As the number of increases, the bond length are the longest bonds (share pair of e - ) o WEAKEST

5 (multiple bonds continued) o BONDS AND ENERGY ACIDS o An acid is a are shorter (share pair of e - ) o INTERMEDIATE Duffey, Chem 215, Unit 8 Notes, p. 5 are the shortest (share pair of e - ) o STRONGEST Bonding involves energy changes: Bond BREAKING is always Bond MAKING is always An endothermic reaction Occurs when a greater amount of energy is to BREAK the bonds than is when new bonds form. An exothermic reaction Occurs when more energy is as new bonds are FORMED than is to break the original bonds. bonded molecular compound that contains one or more that can form cations. When added to the hydrogen(s) are This makes hydronium ions ( ) and the ph The closer the ph is to 0 or 1 the more the solution o Acid Nomenclature and Formulas Binary Acids have at least hydrogen and an anion that ends in Acid name in the form Hydro (root) ic Acid o Example: Oxyacids (contain anions with oxygen in them) Still have at least one o If the anion ends in Acid name in the form (root) ic Acid Example: o If the anion ends in o Acid Formula Writing Practice Hydrochloric Acid Permanganic Acid Hydronitric Acid Carbonic Acid Hypochlorous Acid Acid name in the form (root) ous Acid Example: