Intro to Bonding: Part 2: Covalent Compounds (Type 3 Binary Compounds)

Covalent Bonds A bonding force resulting from the sharing of valence electrons. Covalent compounds result when a nonmetal shares electrons with another nonmetal. Example: – Carbon dioxide (CO 2 ) Carbon (C) is a nonmetal Oxygen (O) is a nonmetal

Valence Electrons Valence electrons are the electrons found in the outermost energy level. The periodic table organizes the number of valence electrons based on the group that the element is located in.

Valence Electrons Valence electrons tell us how many electrons are available for bonding. In covalent bonds, electrons are shared. So the valence electrons are the electrons that are shared in a covalent bond. Valence electrons can be illustrated using a Lewis Dot Structure.

Lewis Dot Structures A representation of a molecule showing how valence electrons are arranged among the atoms in the molecule. Dots are used to represent valence electrons. The dots are written around the element symbol.

Lewis Dot Structures Each atom wants to achieve noble gas electron configuration. To do this, it must complete it’s outermost energy level. For H and He, this means fulfilling the duet rule: having 2 electrons in the outermost energy level.

Lewis Dot Structures For atoms that contain more electrons than H and He, there is the octet rule: having 8 electrons in the outermost energy level. Example: Fluorine gas Each fluorine atom will share 1 electron to satisfy the octet rule. By doing this, both fluorine atoms bond covalently and create a covalent compound.

Steps for Writing Lewis Structures 1.Obtain the sum of the valence electrons from all of the atoms. 2.Use one pair of electrons to form a bond between each pair of bound atoms. Use a line (instead of a pair of dots) to indicate each pair of bonding electrons. 3.Arrange the remaining electrons to satisfy the duet rule for hydrogen and the octet rule for each second-row element.

Single, Double, Triple Bonds By drawing the Lewis dot structure, you can determine if there is a single, double, or triple bond between atoms. Single bond – Each atom shares one electron Double bond – Each atom shares two electrons Triple bond – Each atom shares three electrons.

Single, Double, Triple Bonds Bonds are represented by solid lines:

Nonpolar Covalent Bonds A nonpolar covalent bond is when electrons are shared equally. An example is Oxygen gas – Each oxygen atom has 6 valence electrons – Each oxygen is going to share 2 valence electrons. – Oxygen is left with 2 lone pairs on each oxygen atom. Thus there is an equal distribution of electrons. – Oxygen gas would be a nonpolar covalent compound.

Polar Covalent Bonds A polar covalent bond is when electrons are NOT shared equally. An example is HCl – Hydrogen has 1 valence electron. – Chlorine has 7 valence electrons. – Hydrogen will share it’s one electron so that Chlorine can fulfill the octet rule. – Chlorine will share one of it’s electrons so that Hydrogen can fulfill the duet rule. – Hydrogen is left without any lone pairs. Chlorine has 3 lone pairs. Thus there is an unequal distribution of electrons. – HCl would be a polar covalent compound.