PS Ch. 5 Sec. 3 Notes
How Covalent Bonds Form
*Covalent bonds are when 2 atoms share electrons.
-Covalent bonds usually form between two nonmetals.
(Reminder: Ionic bonds are between a metal and a nonmetal.)
Electron Sharing
*All nonmetals can bond to other nonmetals by sharing electrons
(excluding Noble Gases).
*Nonmetals can even bond to each other.
Ex: F can bond to F and produce F2 (diatomic)
*When you draw their Lewis Dot Structures, you count the shared
electrons twice.
How Many Bonds?
*Nonmetals with 7 ve- can form 1 covalent bond because it only needs 1
ve- to equal 8.
*Nonmetals with 6 ve- can form up to 2 covalent bonds because it needs 2
ve- to equal 8.
*Nonmetals with 5 ve- can form up to 3 covalent bonds because it needs 3
ve- to equal 8.
Double Bonds and Triple Bonds
*When atoms share 2 pairs of electrons = double bond
*When atoms share 3 pairs of electrons = triple bond
Figure 16 on pg. 168
Molecular Compounds
*Compound that is composed of molecules
-These molecules are covalently bonded
*Properties of Molecular Compounds:
-Low melting and boiling points
-Do NOT conduct electricity when dissolved in water
Math Analyzing Data pg. 169
Unequal Sharing of Electrons
*Atoms of some elements pull more strongly on shared electrons than do
atoms of other elements*
-In this case, electrons are pulled closer to 1 atom causing a slight
electrical charge.
*Not as strong as ion charges
Polar Bonds and Nonpolar Bonds
*The atom that has the stronger pull on electrons will result in a negative
charge
*The weaker pull will result in a positive charge
*Polar Bond: covalent bond where electrons are shared unequally
*Nonpolar Bond: covalent bond where electrons are shared equally
Attractions Between Molecules
*The negative ends of polar molecules attract the positive ends of polar
molecules.
Ex: H2O molecules
*In contrast, there is little attraction between nonpolar molecules
Ex: CO2