Ch 7.1 & 7.2 Ionic Bonds Ch 9.1 & 9.2 Names & Formulas of Ionic Compounds Ch 7.3 Metallic Bonds

Valence Electrons  the electrons in the highest occupied energy level/ highest shell of the atom (farthest from nucleus, on the “outside” of the atom)  generally the only electrons involved in bond formation.

Electron Dot Structure or Lewis Dot Diagram A notation showing the valence electrons surrounding the atomic symbol.

Elements within the same group have the same electron-dot structure.

OCTET (or duet) RULE Atoms tend to react (gain, lose, or share electrons) in order to achieve a full valence shell (usually 8 valence electrons, like a noble gas).

When the valence shell is full, the atom is stable, less likely to react. Example: Noble (Inert Gases) Kr A Stable Octet

IONIC BONDING Bonds are formed when e- are fully transferred from METALS to NONMETALS  Electronegativity (EN) between two atoms GREATER THAN 2.0 METAL have low EN  lose e-  cations NONMETAL have high EN  gain e-  anions IONIC BOND = electrostatic attraction between oppositely charged ions (the compound charge overall is neutral)

Example: Which of the following compounds are IONIC? 1.NaCl 2.CO 2 3.CO 4.KF 5.KNO 3 Any formula that contains a METAL!

Ionic Bonds

Example: Formation of Magnesium Nitride MgN[Mg] +2 [ N ] -3 MgN  [Mg] +2 [ N ] -3 Mg[Mg] +2 Mg wants to lose 2 e-; N wants to gain 3e- # of e- lost = # of e- gained SO WANT A MULTIPLE OF 2 & 3 = 6 e- transferred

IONIC NOMENCLATURE

TYPES OF COMPOUNDS BINARY COMPOUNDS -contain only 2 elements (SIMPLE!) TERTIARY/ TERNARY COMPOUNDS -contain 3 or more elements (& POLYATOMIC IONS!!!)

Naming Ionic Compounds, a First Look POSITIVE ION NAME (cation) + NEGATIVE ION NAME (anion) Example: NaFSodium Fluoride Na 2 SO 3 Sodium Sulfite

Naming CATIONS (+). Use the name of the METAL if Group 1, 2, or Ag +1, Cd +2, Zn +2, or Al +3 (IT CAN ONLY HAVE ONE CHARGE!) Example: Na + Sodium ion. Use the name of the METAL followed by a ROMAN NUMERAL INDICATING CHARGE for any other metal BECAUSE IT CAN HAVE MORE THAN ONE CHARGE!!! Example: Fe +2 Iron (II) ion Fe +3 Iron (III) ion

Naming ANIONS (-) Use the name of the NONMETAL with the ending –ide. Example: F - fluoride POLYATOMIC IONS (group of atoms with a charge) Example: SO 4 2- sulfate SO 3 2- sulfite HAVE OXYGEN

Just a note… The “-ITE” form of a polyatomic ion has one less O than the “-ATE” form…

When given the formula, you may need to determine the CHARGE of the metal Pb(SO 4 ) 2 Cu 2 O +4 (x) x 1 (-2) x 2 (x) x 2 (-2) x Lead (IV) sulfate Copper (I) oxide

Writing Ionic Formulas To write a formula for an ionic compound: 1.Write the cation first followed by the anion. 2.Cross the absolute values of the charges so that it becomes the subscript of the other element or polyatomic ion (put polyatomic ions in parentheses) 3.Reduce the subscripts by dividing by a common factor (if possible) THE NET CHARGE OF COMPOUNDS = ZERO!

Examples Ex:Iron (III) sulfideFe +3 O -2 Fe 2 O 3 Ex: Magnesium chlorideMg +2 Cl -1 MgCl 2 Ex:Magnesium chlorateMg +2 ClO 3 -1 Mg(ClO 3 ) 2 - use parentheses when more than one polyatomic ion Ex :Magnesium oxide Mg +2 O -2 Mg 2 O 2  MgO - must reduce!!!

Formula Unit The chemical formula for an IONIC COMPOUND that shows the lowest whole number ratio of the atoms (ions) that results in an overall neutral charge. Example: KCl, Mg Cl 2

The formula unit is used because ionic compounds have a crystalline, lattice arrangement of many, many ions. Which ball represents the Na +1 ? Ex: NaCl The SMALLER purple one!

Ionic CmpdsMolecular Cmpds StructureCrystal lattice of ions Many molecules Types of Elements Metal with non- metal or polyatomic ions Non-metal with non-metal Physical StateSolidSolid, liquid or gas Melting Point High, > 300  CLow, <300  C Solubility in H 2 OGenerally highGenerally low Electrical conductivity of AQUEOUS SOLUTION Good conductorPoor to none Smallest unitFormula unitMolecule

Metallic Bonds Metals consist of closely packed cations floating in a “sea of electrons”. All of the atoms are able to share their valence electrons. The electrons are not bound to individual atoms.

Cations packed in “a sea of electrons”

Properties of Metals Good conductors – Electrons can travel from any position in the metal to another conducting electricity as they move… Ductile/ Malleable - Electrons act as a lubricant, allowing cations to move past each other

Metals have a Crystalline Structure Packed spheres of the same size and shape: – Body Centered Cubic – Face Centered Cubic – Hexagonal Close Packed

Body Centered Cubic Chromium

Face-Centered Cubic Gold

Hexagonal Close-Packed Zinc

Alloys Mixtures of two or more elements, at least one of which is a metal. Made by melting, mixing, then cooling the metals. May contain non-metals like carbon.

Alloys Properties are superior to their components. Sterling silver – 92.5% Ag, 7.5% Cu – Harder than silver Bronze – 7:1 Cu to Sn (tin) Stainless Steel – Fe 80.6%, Cr 18%, C 0.4%, Ni 1% Cast Iron -Fe 96%, C 4%

Types of Alloys Two types of formation: – Substitutional alloys Similar size atoms – replacement – Interstitial alloys Different size atoms – smaller ions fill interstices (spaces between atoms)