Chapter 9 – Covalent Bonding

Review of Chapter 8 In Chapter 8, we learned about electrons being transferred (“given up” or “stolen away”) This type of “tug of war” between a METAL and NONMETAL is called an IONIC BOND, which results in a SALT being formed

Chapter 9.1 – The Covalent Bond In this chapter, you will learn about another type of bond in which electrons are shared Covalent Bonds are atoms held together by SHARING electrons between NONMETALS

Salt vs. Molecules A metal cation and nonmetal anion are joined together by an ionic bond called SALT A group of atoms joined together by a covalent bond is called a MOLECULE A Compound is a group of two or more atoms bonded together (Ionic or Covalent).

Ionic vs. Covalent IONICCOVALENT Bonded NameSaltMolecule Bonding TypeTransfer e - Share e - Types of ElementsMetal & Nonmetal Nonmetals Physical StateSolid Solid, Liquid, or Gas Melting Point High (above 300ºC)Low (below 300 ºC) Solubility Dissolves in Water Varies ConductivityGoodPoor

Properties of Molecular Compounds Lower Melting Points than Ionic Compounds (which means that they are weaker than ionic) Liquids or gases at room temperature

Molecular Formulas The Molecular Formula is the formula of a molecular compound It shows how many atoms of each element a molecule contains Example H 2 O contains 3 atoms (2 atoms of H, 1 atom of O) C 2 H 6 contains 8 atoms (2 atoms of C, 6 atoms of H)

Practice How many atoms total and of each do the following molecular compounds contain? 1. H 2 2. CO 3. CO 2 4. NH 3 5. C 2 H 6 O

Practice: True or False 1. All molecular compounds are composed of atoms of two or more elements. 2. All compounds are molecules. 3. Molecular compounds are composed of two or more nonmetals. 4. Atoms in molecular compounds exchange electrons. 5. Molecular compounds have higher melting and boiling points than ionic compounds.

How to draw Lewis Structures 1. Find the total # of valence electrons 2. Put the least electronegative element in the center (Fluorine = highest EN; Hydrogen ALWAYS on outside) 3. Put two electrons in between atoms to form a chemical bond 4. Complete octets of outer elements 5. If central does not have octet, move electrons from outer atoms to form double or triple bonds.