Covalent Compounds Covalent compounds share electrons to make bonds. These compounds DO NOT involve ions The smallest component of a covalent compound is known as a molecule. Water is an example of a covalent compound.

Covalent Compounds The two electrons shared between each hydrogen atom and the oxygen atom are called bonding pairs. Since there is only one pair of electrons involved in each bond, it is called a single bond. The two pairs of electrons that are not involved in bonds are called lone pairs.

Check Your Understanding Draw the Lewis Structure for ammonia, NH 3 Predict the Formula for the compound formed by oxygen and fluorine.

Check Your Understanding Draw the Lewis Structure for ammonia, NH 3 Predict the Formula for the compound formed by oxygen and fluorine. OR

Multiple Covalent Bonds Sometimes it is necessary to share more than one pair of electrons to achieve an “octet” or complete outer shell of electrons. If two pairs of electrons are shared, this is a double bond.

Multiple Covalent Bonds If three pairs of electrons are shared, this is a triple bond.

Other Ways to Represent Molecules Structural Formulas

Other Ways to Represent Molecules

Ionic vs Covalent PropertyIonicCovalent Bond TypeIonicCovalent Melting PointHighLow Boiling PointVery HighLow Electrical Conductivity when Liquid YesNo

Why? Based on what you understand about ionic and covalent bonds, electrostatic attraction and the molecular kinetic theory of matter, try to explain the properties mentioned on the previous slide.

Why? Ionic Compounds have high melting points Each positive ion is attracted to all the negative ions that surround it Each negative ion is in turn surrounded by positive ions All ions are “attached” to each other by ionic bonds to form a lattice The substance must gain  energy to break all of these ionic bonds. Molecular Compounds have low melting points Covalent bonds are stronger than ionic But, they only hold the atoms together to form molecules The molecules are only held together by intermolecular forces (such as H bonding) These forces are relatively weak

Why is boiling point lower in molecular compounds? Same explanation as melting points: Less energy is needed to overcome the attractive forces between molecules compared with that between ions

Why do ionic compounds conduct electricity better? Electricity is conducted through water by the movement of ions. Molecular compounds do not form ions. Some polar molecular compounds do conduct electricity (Eg. Water) …we will study these later.