CHEMISTRY 111/112 Chapter Eight: Covalent Bonding

Molecular Compounds  So far, we have looked at ionic compounds – composed of a metal and nonmetal, bound together by an ionic bond (electron transfer)  Another type of compound exists that does not exhibit the same properties as ionic compounds  Molecular compounds are composed of nonmetals and share electrons between two nuclei  These shared electrons form a covalent bond

Molecules  A molecule is a neutral group of atoms joined together by covalent bonds  The simplest kind of molecules are diatomic – those consisting of two identical nonmetals  O 2, Br 2, Cl 2  A compound composed of molecules is called a molecular compound  Their physical properties include lower melting points and boiling points than ionic compounds

Molecular Formulas  A molecular formula is the chemical formula of a molecular compound  It shows how many atoms of each element a molecule contains  Ex. H 2 O, CO 2, CCl 4  The subscripts are not necessarily the lowest whole- number ratios

Molecular Structure  The formula does not give any indication of its physical structure  Diagrams and models can be used to help illustrate the way in which such compounds arrange themselves  Figure 8.5, p. 215

True or False 1. All molecular compounds are composed of atoms of two or more different elements. 2. All compounds contain molecules. 3. No elements exist as molecules. 4. Most molecular compounds are composed of two or more nonmetallic elements. 5. Atoms in molecular compounds share electrons. 6. Molecular compounds tend to have higher melting points and boiling points than ionic compounds.

Br 2, KBr, CH 4, SO 3, N 2 H 2, Ne 2  Identify the substance that does not exist.  Identify the ionic compound.  Which formulas represent molecules?  Which formulas represent compounds?  How many atoms are in SO 3 ?

For Wednesday, October 22nd  Assignment on Ions and Ionic Compounds  Questions 3 – 6, pg. 216  Section Review 8.1