Ionic Compounds Ch.6 & 7

Ionic Bonding – strongest of all bonds definiton – results from the electrical attraction between cations (+) and anions (-) “ions” means charges in our case Calculated by the difference between electronegativity values (over 1.7) Figure 2 -- p.176

Ionic Bonding Positive ions are formed from the metal elements when they lose electrons Negative ions are formed from the nonmetal elements when they gain electrons The two, (+) and (-) come together to form a new compound

Ionic Compounds definition – composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal In a neutral compound, the net charge will be zero Balance the charges from cations and anions until the compound is neutral

Forming Ionic Compounds Na+ + Cl-  NaCl Ca2+ + Cl-  CaCl2 Mg2+ + O2-  MgO Fe3+ + S2-  ______ beryllium + iodine  ______

Naming Ionic Compounds Name the metal first (complete name) Name the root of the nonmetal the change the ending to –ide If there is a polyatomic (more than one atom carrying one charge) use the name as it is Transition metals have a Roman numeral after it to tell its charge

Naming Ionic Compounds NaCl ____________________ CaCl2 ____________________ MgO ____________________ Fe2S3 ____________________ BeI2 ____________________

Ionic Compound Characteristics A formula unit is the smallest whole number ratio of cation to anion ex. NaCl Ionic compounds mostly have a crystalline structure Lattice energy is the energy released when one mole of an ionic crystalline compound is formed from gaseous ions Insert the crystalline structure of NaCl

Ionic Compound Characteristics Generally have a high melting point and boiling point Hard but brittle Not electrical conductors as solids Most can dissolve in water Strongest bond

Polyatomic Ions Definition: a charged group of covalently bonded atoms Lewis structures can be used to show the electron placement and where the charge of the ion comes from (p.194)

Polyatomic Ions Names have a system: ending -ate means the highest number of oxygen bonded for that nonmetal (sulfate, chlorate, iodate, etc) ending –ite means one less oxygen than -ate (sulfite, chlorite, iodite, etc) Chlorine is a special case: ClO4-, ClO3-, ClO2-, ClO-, Cl- (p.226)

Polyatomic Ions to Study Phosphate PO4-3 Chlorate ClO3- Nitrate NO3- Sulfate SO3-2 Carbonate CO3-2

Oxidation Numbers Definition: the number of electrons that must be added to or removed from an atom in a combined state to convert the atom into the elemental form Example: H+ + Cl-  HCl KMnO4 K = ___ Mn = ___ O = ___

Oxidation Number Practice NaH Na = _____ H = _____ KClO2 K = ____ Cl = ____ O = ____ KClO3 K = ____ Cl = ____ O = ____

Metallic Bonding Definition: the chemical bonding that results from the attraction between two metal atoms and the surrounding sea of electrons Properties include: High electrical and thermal conductivity Strong absorber and reflector of light Conforms to shape easily Malleability – hammered into sheets Ductility – drawn into wires

Covalent Molecules Ch. 6 & 7

Covalent Bonding Definition: bond formed by the sharing of electron pairs between two nonmetals There are two types of covalent bonds: Nonpolar: electrons are shared equally Polar-covalent: unequally shared electrons

Electronegativities Every element on the PT has an electronegativity value Those values are subtracted to see whether is: Nonpolar (0-0.3) Polar-covalent (0.3-1.7) Ionic (over 1.7)

Lewis Structures Definition – formulas in which atomic symbols represent nuclei and inner-shell electrons, dot-pairs in covalent bonds Sample Problem C - p.185 Practice - p.186

Molecular Geometry VSEPR theory – repulsion between the sets of valence electrons surrounding an atom causes these sets to be oriented as far as possible Use VSEPR with Lewis structures to come up with shapes Shapes are: Linear, trigonal planar, tetrahedral, bent, and trigonal pyramidal, etc. (p.200) Sample Problem F – p.201

Intermolecular Forces Definition: forces in between molecules Weaker than bond strength Types: Dipole-dipole: strongest in polar covalent Hydrogen bonding: hydrogen bonded to highly electronegative atom London dispersion forces: weakest force due to motion of atoms in compound

Naming Covalent Molecules Use prefixes listed on p.228 Prefixes tell how many atoms of each nonmetal make up the molecule The nonmetal farthest left on PT is written first, then the most electronegative atom (farthest right on the PT) Mono does not appear on the first atom to notate one, it is understood Omit vowels on the prefix if there is a vowel on the element Second atom ends in -ide

Covalent Prefixes mono 1 di 2 tri 3 tetra 4 penta 5 hexa 6 hepta 7 octa 8 nona 9 deca 10 Two Rules of Thumb: If two vowels end up next to each other, the vowel on the prefix will be deleted. Mono is never used for the first element.

Practice Name the following covalent compounds: CO2 _________________ OF3 _________________ SO2 _________________

Acids Formed from H+ + a nonmetal or a polyatomic If H+ is bonded to a nonmetal, use the prefix hydro- + the root of the nonmetal + ending with –ic acid If H+ is bonded to a polyatomic, do NOT use the prefix hydro! Use the root of the polyatomic and use ending from –ate to –ic or –ite to –ous acid Section Review p.231 #4 f-h

Practice Name the following acids: HCl ________________ HClO4 ________________ H2SO3 ________________ HI ________________