Chemical Bonding and Nomenclature

Chemical Bond Mutual electrical attraction between the nuclei and valence electrons of different atoms Atoms bond to reduce potential energy Atoms become more stable when they are bonded

Types of Chemical Bonds Metallic – Attraction between metal atoms and the surrounding electrons Ionic – Electrical attraction between cations and anions Covalent – Sharing of electrons between atoms Nonpolar Covalent – Electrons are shared equally between the atoms Polar Covalent – Electrons are not shared equally between the atoms

Metallic Bonding Empty d orbitals are overlapping – electrons flow between these empty orbitals creating a ‘sea of electrons’ A network of metal atoms forms in which the atoms attract the ‘sea of electrons’

Metals have Unique Properties High electrical conductivity Absorb and emit light – shiny Malleable – can be hammered into thin sheets (Layers of atoms just slide past one another) Ductile – can be drawn into a string

Ionic or Covalent??? Check the electronegativity difference between two atoms… If the EN difference is greater than 1.7, the bond will be ionic. If the EN difference is 0.3 to 1.7, the bond is polar covalent If the EN difference is 0 to 0.3, the bond is nonpolar covalent

Ionic Bonding Cation transfers electrons to anion Creates a crystalline solid – 3-D network of cations and anions Lowest ratio of the cations to anions is represented by the formula unit

Formation of Ionic Compounds Electron-dot notation – represents transfer of electrons

Example Draw the electron dot diagram representing the formation of an ionic bond between potassium and iodine aluminum and oxygen

Characteristics of Ionic Bonds Ions have strong attractions between them – this results in: High melting point, high boiling point Hard, but brittle Layers of ions will break apart Only electrical conductors in molten state Many ionic compounds will dissolve in water

Things to know about ions before naming/writing ionic formulas Cations can be monatomic or polyatomic ions Monatomic charges are on the PT and polyatomic ions must be memorized (p. 210 of textbook) Cations can also be transition metals – lose a varying amount of electrons – must use Roman numerals to indicate charge Exceptions: Zn+2, Cd+2, Ag +1 Lead and Tin also use Roman numerals to indicate charge Anions can be monatomic or polyatomic ions

Practice - Naming Ions Write the names the following ions: Ca+2 I-1 Cu+2 Zn+2 Pb +4 NO3-1 NH4+1

Answers Calcium Ion Iodide Copper (II) Zinc Lead (IV) Nitrate Ammonium

Ionic Nomenclature To name an Ionic Compound Step 1: Name the cation Check to see if it needs Roman numerals Step 2: Name the anion

Examples NH4Cl NaBr CaI2 (NH4)2SO4 K2O Pb(ClO3)4 CuCl BaSO3 CuCl2 MnO ZnBr2 K2SO4 Ca(NO3)2 NH4Cl (NH4)2SO4 Pb(ClO3)4 BaSO3 MnO AgCl

Answers Sodium bromide Calcium iodide Potassium oxide Copper (I) chloride Copper (II) chloride Zinc bromide Potassium sulfate Calcium nitrate Ammonium chloride Ammonium sulfate Lead (IV) chlorate Barium sulfite Manganese (II) oxide Silver chloride

Writing Ionic Formulas To write an ionic compound’s formula Step 1: Write the formula for the cation – including charge Step 2: Write the formula for the anion – including charge Step 3: Balance the charges. Be sure to use parenthesis if more than one polyatomic ion is needed

Examples Calcium chloride Barium sulfide Ammonium nitride Iron (II) chloride Lead (IV) sulfate Barium phosphate Calcium hydroxide Iron (III) permanganate Ammonium nitrite Calcium carbonate Copper (II) sulfate Sodium acetate Potassium sulfite Sodium hydroxide

Acid Nomenclature The first element is Hydrogen – H____ To name an acid, look at the anion: If the anion ends in –ide, change the name of the acid to hydro-ic acid If the anion ends in –ite, change the name of the acid to –ous acid. If the anion ends in –ate, change the name of the acid to –ic acid.

Examples HCl H2SO4 HClO3 HBr H2S HClO4 H2CO3 HNO2

Answers Hydrochloric acid Sulfuric acid Chloric acid Hydrobromic acid Hydrosulfuric acid Perchloric acid Carbonic acid Nitrous acid

Acids – Writing Formulas To write the formula for an acid Step 1: Decide which ion is needed based on the ending Step 2: Add H+1 in front of the anion Step 3: Balance the charges

Examples Hydroiodic acid Phosphorous acid Sulfurous acid Nitric acid Acetic acid Phosphoric acid Hypochlorous acid

Answers HI H3PO3 H2SO3 HNO3 HCH3COO or CH3COOH H3PO4 HClO