Classifying Chemical Compounds Chemical Bonding Classifying Chemical Compounds

Bond Types Atoms can combine to form compounds of two bond types: Ionic Compounds Covalent Compounds Ex: NaCl Ex: CO2

Physical Properties – Comparison Property Ionic Compound Covalent Compound State at room temperature Melting point Electrical conductivity as a liquid Solubility in water Electrical conductivity when dissolved in water

Physical Properties – Comparison Property Ionic Compound Covalent Compound State at room temperature Crystalline solid liquid, solid, gas Melting point Electrical conductivity as a liquid Solubility in water Electrical conductivity when dissolved in water

Physical Properties – Comparison Property Ionic Compound Covalent Compound State at room temperature Crystalline solid liquid, solid, gas Melting point High Low Electrical conductivity as a liquid Solubility in water Electrical conductivity when dissolved in water

Physical Properties – Comparison Property Ionic Compound Covalent Compound State at room temperature Crystalline solid liquid, solid, gas Melting point High Low Electrical conductivity as a liquid Yes No Solubility in water Electrical conductivity when dissolved in water

Physical Properties – Comparison Property Ionic Compound Covalent Compound State at room temperature Crystalline solid liquid, solid, gas Melting point High Low Electrical conductivity as a liquid Yes No Solubility in water High solubility (for most) Low solubility (for most) Electrical conductivity when dissolved in water

Physical Properties – Comparison Property Ionic Compound Covalent Compound State at room temperature Crystalline solid liquid, solid, gas Melting point High Low Electrical conductivity as a liquid Yes No Solubility in water High solubility (for most) Low solubility (for most) Electrical conductivity when dissolved in water Not usually

Chemical Properties – Comparison Bonds form when the valence e- of atoms interact. Atoms can either exchange e- or share e- There are two types of chemical bonds

Ionic Bonding When 2 atoms exchange (or transfer) electrons 1 atom loses an e- 1 atom gains an e- metal non-metal lose gain

Covalent Bonding When 2 atoms share electrons Usually forms between 2 non-metals

Electronegativity Recall: Electronegativity (EN) is a measure of an atom’s ability to attract electrons in a chemical bond. When 2 atoms form a bond, each atom attracts the other’s electrons in addition to its own.

Table – Electronegativity Values

Predicting Bond Type Using EN The difference between EN values (EN) for the 2 atoms in a bond can be used to predict bond type. Ex: CaF2 EN = ? Chemical bonds range from mostly ionic to mostly covalent.

Predicting Bond Type Using EN EN values 3.3 1.7 0.5 0 mostly polar mostly ionic covalent covalent

Predicting Bond Type Using EN - Examples i) calcium fluoride EN = CaF2 ii) hydrogen chloride EN = HCl iii) methane EN = CH4 iv) oxygen EN = O2

Chemical Bonding Bond Formation

Covalent Bonding Involves sharing of e- Sharing of e- between atoms may not be equal. non-polar covalent (mostly covalent) bond involves equal sharing polar covalent bond involves unequal sharing

Covalent Bonding-Example water (H2O) EN = 1.24 This is polar covalent bond (unequal sharing) The O end of the H-O bond has a partial negative charge (-) while the H end of the bond has a partial positive charge ( +) This separation of charges makes a dipole ( +   -)

Polar Bonds Using EN values you can predict the polarity of a bond. The overall polarity of a molecule depends on a combination of: the polarity of the bonds the shape of the molecule

Shapes of Molecules To illustrate the shape of the molecule using a Lewis diagram: Determine the “central atom” , i.e. the atom requiring the most electrons. Determine how many electrons each atom needs to gain in order to become isoelectronic with its closest noble gas. Determine if multiple bonds are needed. Determine the structural shape of the molecule based on # atoms bonded to central atom # lone pairs of electrons (see handout of molecular shapes)

How Does That Look Again? Shapes of Molecules

Shapes of Molecules-Examples Chemical formula Lewis diagram Structural diagram Shape CH4 methane CO2 H2O

Polarity of Molecules To predict the polarity of the molecule: Determine if there are polar bonds using EN value If there are polar bonds, establish the direction of the dipoles. (A dipole exists when two opposite charges are separated by a short distance) ( +   -)

Polarity of Molecules iii. Once you identify the shape of the molecule   if the dipoles cancel due to the shape of the molecule then the compound is non-polar if the dipoles do not cancel due to the shape of the molecule then the compound is polar

Polarity of Molecules-Examples Chemical formula Lewis diagram Structural diagram (include dipoles) Shape Polarity of molecule (polar/ non-polar) CH4 methane CO2 H2O

Video Clip Polar Bonding

Chemical Formulas - Ionic Chemical Bonding Chemical Formulas - Ionic

Writing Formulas–Binary Compounds contain H, metal or metalloid with only 1 oxidation number (or valence) (see periodic table for values) name the first element and change the ending (suffix) of second element to “ide” Use zero sum rule to write formula Try Table 1

Chemical Formulas - Practice Table 1 Br1- N3- K1+ Mg2+ Al3+ K2S KBr K3N potassium sulfide potassium bromide potassium nitride Mg3N2 magnesium nitride MgS magnesium sulfide MgBr2 magnesium bromide Al2S3 aluminum sulfide AlBr3 aluminum bromide AlN aluminum nitride

Tertiary Compounds contain polyatomic ions (see periodic table given in class) name the first element and then the polyatomic ion Use zero sum rule to write formula Try Table 2

Chemical Formulas - Practice Table 2 OH1- CO32- PO43- Mg2+ Li1+ NH41+ hydroxide carbonate phosphate Mg(OH)2 MgCO3 magnesium carbonate Mg3(PO4) 2 magnesium phosphate magnesium hydroxide LiOH lithium hydroxide Li2CO3 lithium carbonate Li3PO4 lithium phosphate (NH4)2CO3 ammonium carbonate NH4OH ammonium hydroxide (NH4)3PO4 ammonium phosphate ammonium

Writing Formulas – Multivalent Ions When the first element has more than 1 oxidation number (or valence) IUPAC System (Stock System) Use Roman numeral to indicate valence of more electronegative element Ex: Cu1+ copper (I) Cu2+ copper (II) Note: Hg2+ mercury (II) Hg22+ (Hg1+)mercury (I)

Writing Formulas – Multivalent Ions Old system(Classical System)(ic/ous) Use suffix “ic” for highest valence and “ous” for lowest Use classical name of element (see table provided on next slide)

Table: Multivalent Ion Names Formula IUPAC Name Classical Name Cu1+ copper (I) Cu2+ copper (II) Fe2+ iron (II) Fe3+ iron (III) Hg22+ (Hg1+) mercury (I) Hg2+ mercury (II) Pb2+ lead (II) Pb4+ lead (IV) Sn2+ tin (II) Sn4+ tin (IV) Cr2+ chromium (II) Cr3+ chromium (III) Mn2+ manganese (II) Mn3+ manganese (III) Mn4+ manganese (IV) Co2+ cobalt(II) Co3+ cobalt(III) Au1+ gold (I) Au3+ gold (III) Table: Multivalent Ion Names

Table: Multivalent Ion Names Formula IUPAC Name Classical Name Cu1+ copper (I) cuprous Cu2+ copper (II) cupric Fe2+ iron (II) ferrous Fe3+ iron (III) ferric Hg22+ (Hg1+) mercury (I) mercurous Hg2+ mercury (II) mercuric Pb2+ lead (II) plumbous Pb4+ lead (IV) plumbic Sn2+ tin (II) stannous Sn4+ tin (IV) stannic Cr2+ chromium (II) chromous Cr3+ chromium (III) chromic Mn2+ manganese (II) Mn3+ manganese (III) Mn4+ manganese (IV) Co2+ cobalt(II) cobaltous Co3+ cobalt(III) cobaltic Au1+ gold (I) aurous Au3+ gold (III) auric Table: Multivalent Ion Names

Chemical Formulas - Practice Table 3 IUPAC Old System FeCl2 FeCl3 copper (I) fluoride nickel (II) sulfide ferric oxide mercuric oxide iron (II) chloride ferrous chloride iron (III) chloride ferric chloride CuF cuprous fluoride NiS nickelous sulfide Fe2O3 iron (III) oxide HgO mercury (II) oxide

Writing Formulas – Polyatomic Ions Some polyatomic ions contain the same types of atoms but different numbers of each type. (see periodic table given in class)

Writing Formulas – Polyatomic Ions For the related ions, only the “ate” ions need to be memorized, others may be found following this pattern: Step method:

Writing Formulas – Polyatomic Ions For the related ions, only the “ate” ions need to be memorized, others may be found following this pattern: Step method: As you move up one step…the # of oxygen atoms increases by 1 Charge on ion stays the same hypo ite ate per

Oxy-Acid Radicals Try the oxy-acid radicals handout provided Note: Elements in the same group on the periodic table form the same polyatomic ion.

Chemical Formulas - Covalent Chemical Bonding Chemical Formulas - Covalent

Covalent Compounds-Prefix Method When compounds contain 2 non-metals use the PREFIX METHOD for naming. Write the name of the 1st element the first element is the least electronegative element (i.e. closest to the LHS of the periodic table) Write the name of the 2nd element deleting the last few letters and adding “ide” Indicate the # atoms of each type with the appropriate prefix See p105 Table 3.8 (copy this) Note: “mono” is left out when there is a single atom of the first element.

Number Prefix 1 mono- 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 7 hepta- 8 octa- 9 nona- 10 deca-

Examples S2O3 N2O5 CF4 silicon monoxide diphosphorus tetroxide CO2 CO   N2O5 CF4 silicon monoxide diphosphorus tetroxide CO2 CO   Al2O3 disulfur trioxide dinitrogen pentoxide carbon tetrafluoride SiO P2O4 carbon dioxide carbon monoxide aluminum oxide (IONIC - METAL!)

Hydrides These are binary compounds that contain Hydrogen If H is less electronegative, then it is placed first in the name of the compound hydrogen ion (cation) combines with non-metal but acts like a metal itself H  H1+ + e- e.g. H2Se hydrogen selenide “metal” non-metal HCl hydrogen chloride

Hydrides Sometimes H can act like an anion (usually with a Group 1 metal)… so it is placed second in the name of the compound H + e-  H1- e.g. NaH sodium hydride CaH2 calcium hydride

Hydrides Hydrogen containing compounds can also be formed with Family VA elements…but these are usually referred to by common names rather than IUPAC e.g. NH3 PH3 AsH3 ammonia phosphine arsine

Acids Many compounds that contain H when dissolved in water are also acids e.g. H2SO4 H2SO4(aq) HCl HCl(aq) Recall: physical states (s) (l) (g) (aq) hydrogen sulfate sulfuric acid hydrogen chloride hydrochloric acid

Other Acids? CH3COOH(aq) or HC2H3O2 (aq) H2CO3(aq) HCl(aq) HNO3(aq) Some common ones that you should know acetic acid carbonic acid hydrochloric acid nitric acid sulfuric acid CH3COOH(aq) or HC2H3O2 (aq) H2CO3(aq) HCl(aq) HNO3(aq) H2SO4(aq)