2.2 Molecular Elements and Compounds

Molecular Element: consists of molecules containing atoms of only one type of element Molecular Compound: made up of molecules, each with the same arrangement of specific atoms each molecule is made up of at least 2 elements

diatomic molecule: a molecule consisting of two atoms of the same or different elements carbon monoxide, CO hydrogen gas H2 polyatomic molecule: a molecule consisting of more than two atoms of the same or different elements ammonia, NH3 Sulfur, S8

Properties of Molecular Compounds 1)  Covalent compounds generally have much lower melting and boiling points than ionic compounds.  2)  Covalent compounds are soft compared to ionic compounds- no crystal lattice covalent compounds have molecules which can very easily move around each other, because there are no bonds between them.  As a result, covalent compounds are frequently flexible rather than hard.

3) Generally more flammable than ionic compounds 3) Generally more flammable than ionic compounds. 4) Don't conduct electricity in water. 5) Usually very insoluble in water. 6) Exist is a variety of forms ie. Solids, liquids and gases

Formation of a Covalent Bond arises from the simultaneous attraction of two nuclei for a shared pair of electrons We can represent covalent bonds using Lewis Dot diagrams in the same way we use them for ionic bonds

A covalent bond can consist of two, four, or six electrons depending on the element(s) involved A single bond A double bond A triple bond bonding capacity: the number of electrons lost, gained, or shared by an atomwhen it bonds chemically

structural formula: a representation of the number, types, and arrangement of atoms in a molecule, with dashes representing covalent bonds 1 (a) Draw the Lewis structure for a molecule of oxygen. (b) Give the structural formula for the molecule.

2 (a) Draw the Lewis structure for a molecule of nitrogen. Give the structural formula for the molecule

3 (a) Draw a Lewis structure for a molecule of carbon dioxide. (b) Give the structural formula for the molecule

Try It!- Pg. 65 # 1

Coordinate Covalent Bonds a covalent bond in which both of the shared electrons come from the same atom Polyatomic ions are an example of compounds that contain coordinate covalent bonds

The Strength of Covalent Bonds Covalent bonds are strong large amount of energy is needed to separate the atoms do not easily decompose upon heating triple bonds are stronger than double bonds, which are stronger than single bonds between the same two atoms

Drawing Lewis Structures and Structural Formulas for Molecular Compounds Draw the Lewis structure for PO43-

Try It! Pg. 67 #2