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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 O2, Br2, Cl2
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. H2O, CO2, CCl4
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.
Br2, KBr, CH4, SO3, N2H2, Ne2
Identify the substance that does not exist.
Identify the ionic compound. Which formulas represent molecules? Which formulas represent compounds? How many atoms are in SO3?
For Wednesday, October 22nd Assignment on Ions and Ionic
Compounds
Questions 3 – 6, pg. 216
Section Review 8.1