Section 3 – Covalent Bonds Pg 192 Chapter 5 Section 3 – Covalent Bonds Pg 192

How Covalent Bonds Form Pg 193 How Covalent Bonds Form Covalent Bond: the chemical bond formed when two atoms share electrons Usually between nonmetals

Pg 193 Electron Sharing The force that holds atoms together in a covalent bond is the attraction of each atom’s nucleus for the shared pair of electrons Molecule: a neutral group of atoms joined by covalent bonds

How many Bonds? Like in Water -> Pg 193 The # of covalence bonds that a nonmetal atom can form equals the number of electrons needed to make a total of 8 Oxygen has 6 valence electrons -> needs 2 so can form 2 covalence bonds Like in Water -> Pg 193

Double Bond and Triple Bond Double Bond: two atoms share two pairs of electrons Triple Bonds: atoms share three pairs of electrons Pg 194

Molecular Compounds Pg 194 Molecular Compound: a compound that is composed of molecules Contains atoms that are covalently bonded Compared to ionic compounds, molecular compounds generally have lower melting points and boiling points Also do not conduct electric current when melted or dissolved in water

Low melting point and boiling point Pg 194 Low melting point and boiling point The forces between molecules are much weaker than the forces between ions in an ionic solid Takes less energy to break apart

Poor Conductivity Molecular compounds do not conduct electric current Pg 195 Poor Conductivity Molecular compounds do not conduct electric current No charged particles are available to move (all locked up in bonds) Used to insulate wires Even as liquid, does not conduct electric current Pure water does not conduct electric current

Unequal Sharing of Electrons Pg 195 Unequal Sharing of Electrons Atoms of some elements pull more strongly on shared electrons than other elements Unequal sharing of electrons causes the bonded atoms to have a slight electrical charge

Polar Bonds and Nonpolar Bonds Polar Bond: a covalent bond in which electrons are shared unequally Nonpolar Bond: a covalent bond in which electrons are shared equally Pg 196

Polar Bonds in Molecules Pg 196 Polar Bonds in Molecules A molecule is considered polar if it has a positively charged end opposite a negatively charged end Carbon Dioxide is nonpolar because of its linear shape

Attractions Among Molecules Pg 196 Attractions Among Molecules The properties of polar and nonpolar compounds differ because of differences in attractions between molecules Properties like viscosity!

Chapter 5 Section 3 Homework – pg 197

1A. What is the attraction that holds two covalently bonded atoms together?

1B. A carbon atom can form four covalent bonds 1B. A carbon atom can form four covalent bonds. How many valence electrons does it have?

1C. What is a double bond?

2A. How are the properties of molecular compounds different from those of ionic compounds?

2B. Why are most molecular compounds poor conductors?

3A. How do some atoms in covalent bonds become slightly negative or slightly positive? What type of covalent bonds do these atoms have?

3B. Both carbon dioxide molecules and water molecules have polar bonds 3B. Both carbon dioxide molecules and water molecules have polar bonds. Why then is carbon dioxide a nonpolar molecule while water is polar molecule?

3C. Predict whether carbon dioxide or water would have a higher boiling point.