SOL Review 3 Bonding and Naming Ionic and Covalent Compounds

What are some characteristic differences between ionic and molecular compounds? Ionic Compounds Crystalline at room temperatures Have higher melting points and boiling points compared to covalent compounds Conduct electrical current in molten or solution state but not in the solid state Molecular Compounds Tend to be liquids or gases at room temperature Varies, but usually low melting and boiling points Cannot conduct electricity when dissolved in water

A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical bonds H2H2 H2OH2ONH 3 CH 4 A diatomic molecule contains only two atoms H 2, N 2, O 2, Br 2, HCl, CO A polyatomic molecule contains more than two atoms O 3, H 2 O, NH 3, CH 4 2.5

Ionic Bonds These bonds form when a positively charged cation is attracted to a negatively charged anion. Composed of a metal and a nonmetal. Although they are composed of ions, ionic compounds are electrically neutral (the charges of the cations must cancel out the charges of the anions).

A monatomic ion contains only one atom A polyatomic ion contains more than one atom 2.5 Na +, Cl -, Ca 2+, O 2-, Al 3+, N 3- OH -, CN -, NH 4 +, NO 3 -

Chemical Formula/Formula Units A chemical formula is the type and number of atoms in the smallest unit of the substance. Ionic compounds do not exist as single units, they are a collection of positive and negative ions arrange in a repeating pattern (crystal). We use the term formula unit to indicate the lowest whole number ratio of ions in an ionic compound (NaCl and MgBr 2 are formula units)

Determining the formula of an ionic compound (the formula unit) Cross and drop

Chemical Nomenclature Ionic Compounds - A metal (cation) + nonmetal (anion) -Either the cation or anion may be a polyatomic ion To Name an ionic compound : 1. Name the cation 2. Name the anion, changing the ending to “ide” if monoatomic. If polyatomic anion, just use the polyatomic ion name. BaCl 2 → Barium chloride Na 3 PO 4 → Sodium phosphate 2.7

Transition metal ionic compounds –Transition metals can form more than one cation, with different ionic charges – We indicate the charge on these metals with Roman numerals FeCl 2 2 Cl - = -2, so Fe is +2 iron(II) chloride FeCl 3 3 Cl - = -3, so Fe is +3 iron(III) chloride Cr 2 S 3 3 S -2 = -6, so Cr is +3 chromium(III) sulfide 2.7

Practice Determine what ionic compound is formed from the following combinations of elements, and name the compound. 1.Ba and F2. Mg and PO 4 (Ba 2+ and F - ) (Mg 2+ and PO4 3- ) BaF 2 Mg 3 (PO 4 ) 2 3.Al and O 4. NH 4 and Cl (Al 3+ and O 2- ) (NH 4+ and Cl - ) Al 2 O 3 NH 4 Cl

The Covalent Bond Atoms can form molecules by sharing pairs of electrons in a covalent bond. This is done only among non-metal atoms.

Covalent Bonding Covalent bonds can be single, double, and triple. It is not possible to form a "quadruple" bond! Single covalent bond - each atom contributes one electron to the bond and atoms share one pair. Double bond - two pairs of electrons are shared Triple bond - three pairs are shared.

Naming covalent compounds is different than naming ionic compounds. This is because unlike ionic compounds where 2 elements usually form only one compound, two nonmetals can often form many covalent compounds in different combinations: NON2ON2ONO 2 NO 5 N2O4N2O4

Prefixes are used to indicate the number of atoms of each element in the compound. 1 mono- 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 7 hept- 8 octa- 9 nona- 10 deca-

HIhydrogen iodide NF 3 nitrogen trifluoride SO 2 sulfur dioxide N 2 Cl 4 dinitrogen tetrachloride NO 2 nitrogen dioxide N2ON2Odinitrogen monoxide Molecular Compounds 2.7

The prefixes may only be used with covalent compounds, never ionic compounds!!!!

Molecular Geometry The Valence-Shell Electron Pair Repulsion theory (VSEPR theory) predicts the actual geometrical shape of a molecule : Electron pairs spread out as far as possible in a molecule to minimize the repulsion between negative electron clouds and thus stabilize the molecule.

Molecular Shapes … Which shape is: H 2 O? (bent) _______________ CH 4 ? (tetrahedral) ______________________ CO 2 ? ( linear)