Ionic Bonding and Formulas Unit 5 Ionic Bonding and Formulas

Bond Types Ionic: transfer of electrons Generally forms between metal and a nonmetal (or contains a polyatomic ion): large difference in electronegativity causes electron(s) to be given to more electronegative element Covalent: sharing electron pair(s) Generally forms between nonmetals Metallic: delocalized electrons Always forms between metal atoms

Ionic Bonds Characteristics: High melting point Conduct electricity in molten state and in water solution (dissolved) Held together by electrostatic force (+ to -) Ions pack together in a 3-d stucture called a lattice. The smallest particle of an ionic compound is called a formula unit. This is the simplest ratio of ions in the lattice.

Polyatomic Ions Covalently bonded inside the ion, but charged If it is a part of an ionic compound, there is also an ionic bond between the polyatomic ion and the other ion(s) in the formula. Example: The carbonate ion is CO32-. There are covalent bonds between the C and the three O atoms in the ion. But since it has a -2 charge it can be attracted to positively charged ions such as Ca2+ to form calcium carbonate - CaCO3

Metallic Bonds Characteristics High melting point Luster (shiny) Malleable, ductile (pull into wire) High electrical conductivity & conducts heat Form crystals as solid

Delocalized electrons Outer electrons overlap as atoms crowd together: the electrons move easily and are not held in place (delocalized). This allows: Current to flow Interaction with light (shine) Rearrangement of atoms when pounded or stretched. The number of outer electrons determine the properties Example: hardness of metal In general, the greater the number of outer electrons, the harder the metal. Hardness can be increased by making an alloy (2 or more metals combined)

Formula Subscripts British Association for the Advancement of Science (1863) Tells the number of atoms of the element Examples: H2O means 2 atoms of H, 1 atom of O Al(NO3)3 means 1 atom Al, 3 atoms N, 9 atoms O

Ions Charged particles (cations +, anions -) Monatomic – one atom (most can be predicted by placement in the table because of valence electron configuration)

Many Different Charges General Charges +1 +2 +3 +4 +2 -3 -2 -1 N O B L E G A S Many Different Charges Many Different Charges

Monatomic Ion Examples Group 1 loses its 1 valence electron = +1 charge. Na+ Al Group 13 loses its 3 valence electrons = +3 charge. Al3+ O Group 16 gains 2 electrons to complete octet = -2 charge O2- Cl Group 17 gains 1 electron to complete octet = -1 charge. Cl-

Transition Metal Ions Transition metals and metals in Groups 14 & 15 have the charge listed as a Roman numeral in parentheses as part of the compounds’s name, i.e. copper (II) chloride, because they can have more than one possible charge (oxidation state) Silver (Ag) and zinc (Zn) ONLY have one possible charge so a Roman numeral will not be given. Memorize that silver is +1 and zinc is +2. (Make flashcards of these two and put with polyatomics)

Know the ones on your flashcards for the test! Some other polyatomics that you should know or be able to use are on pages 221 and 970 of your book. Know the ones on your flashcards for the test! MEMORIZE by reviewing several times a day!!

Writing Ionic Formulas A. Compounds are electrically neutral: charges must add to zero (# + charge = # - charge) Cation (+) is written first followed by the anion (-) Binary Examples: calcium chloride, aluminum oxide, barium sulfide, sodium phosphide (see board) Complex compounds: contain a polyatomic ion (use parentheses for more than one) Complex Examples: calcium sulfate, calcium phosphate, aluminum hydroxide, ammonium carbonate (see board)

Naming Compounds Roman Numeral Here too! JUST NAME J U S T N A M E N O B L E G A S Roman Numeral Here too! Ion – change ending to –ide Non-metal bonded with non-metals need mono-, di-, tri-, tetra-, … Prefixes on both! JUST NAME You must use Roman Numeral (I, II, II, IV, …) that tells the charge of the metal, to name a transition metal with a non-metal. You must use Roman Numeral (I, II, II, IV, …) that tells the charge of the metal, to name an inner transition metal with a non-metal.

Acids Memorize the formula and name for the following acids: (MAKE FLASHCARDS and add to your pack) Hydrochloric acid – HCl Nitric acid – HNO3 Sulfuric acid – H2SO4

Naming a compound with a metal from group 1, 2 or 13 and a non-metal (not including H) Just name the metal Name the second element (non-metal), changing the ending to –ide. EXAMPLE: Li2O lithium oxide

Naming a compound with a transition metal and a non-metal Name the metal. Find the charge on the metal ion by using the known charge of the non-metal ion. Work backwards to + charge. Write the charge of the metal as a Roman numeral. Then write the name of the non-metal changing the ending to –ide. Example: CuCl2 Cl is -1. The two of them equal -2, so the copper ion must be +2 to balance copper (II) chloride

Naming a complex compound (contains a polyatomic ion) Name the metal – find the charge and add Roman numeral if needed Name the polyatomic ion Example: Fe2(SO3)3 iron (III) sulfite Name the nonmetal – change ending to –ide Example: NH4Br ammonium bromide