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Iodine monochloride

Since each single bond (represented by a line) contains 2 shared electrons, 8 electrons have already been added to the Lewis structure. As determined in step 1, the molecule contains 32 valence electrons total. Thus, there are 24 more electrons (32-8=24) to add to the Lewis structure.

C already satisfies the octet rule.

Placing the remaining 24 valence electrons around the chlorine atoms satisfies the octet rule for each Cl. The lone pairs are represented by pairs of dots.

Step 4) Check your work: ensure the duet and octet rules are satisfied and count the total number of valence electrons. Review the molecule to ensure that all atoms are surrounded by 8 valence electrons, satisfying the octet rule. Ensure that hydrogen atoms (when present) satisfy the duet rule. Count the number of electrons represented in your diagram. Ensure that the number of elec- trons you count matches the number calculated in step 1.

Example 2: Oxygen gas (O2)

Step 1) Calculate the total number of valence electrons in the molecule.

Oxygen atoms have 6 valence electrons, and there are a total of 2 atoms. There are 12 valence electrons total. 8 ©Hands-On Labs, Inc.

Experiment Molecular Modeling and Lewis Structures

Step 2) Arrange atoms and create single bonds.

The two oxygen atoms should be placed in a line and linked with a single bond that represents shared electrons.

Step 3) Calculate the number of remaining valence electrons; then distribute the electrons with the goal of satisfying the duet rule or octet rule.

Two electrons (held in 1 single bond) have already been added to the Lewis structure. This molecule has 12 valence electrons total, as determined in step 1. Ten more electrons must be added, and this can be accomplished through a trial-and-error process. Creating a double bond between the atoms and then adding lone pairs satisfies the octet rule for all atoms and also generates the correct number of valence electrons. (Double bonds represent 4 shared electrons.)

Consider the outcome if the Lewis structure was drawn with a single bond, and the octet rule was fulfilled. The total number of electrons would be 14. In step 1, we determined that the molecule has 12 valence electrons, so we know that the Lewis structure below is incorrect, even though the octet rule is fulfilled.

Consider the outcome if the Lewis structure was drawn with the correct number of total valence electrons and a single bond. The Lewis structure below is incorrect because, although 12 electrons are present, the octet rule is not fulfilled.

Note: Multiple bonds are used ONLY when there are not enough lone pairs present for each atom to fulfill the octet rule. In the incorrect Lewis structure above, we know a multiple bond is needed because the correct total valence electrons are present but the octet rule is not fulfilled.