Problem 6 - Chemistry A Guided Inquiry

Question

Make a checklist that can be used to determine if a Lewis structure for a molecule is correct.

Step-by-Step Solution

Answer

A valid Lewis structure ensures correct atomic connectivity, proper electron count, octet rule adherence for all atoms except hydrogen, accurate depiction of covalent bonding, zero formal charge on the molecule, and justification for any resonance forms.

Step 1: Verify Atomic Connectivity

The first step is to verify that the atoms are connected in the same order described in the molecule's formula. Often, but not always, the atom named first is in the center, with the other atoms surrounding it.

Step 2: Count All Electrons

Count the total number of valence electrons from all atoms. This total must balance with the sum of valence electrons drawn in the Lewis structure.

Step 3: Check Octet Rule

Verify that all atoms in the molecule (except hydrogen, which requires only two electrons) have an octet of electrons (i.e., eight electrons in their outermost shell). These electrons can be in the form of lone pairs or they can be shared in covalent bonds.

Step 4: Confirm Covalent Bonding

Check that each covalent bond accurately reflects the sharing of an electron pair between two atoms.

Step 5: Assess Formal Charge

Calculate the formal charge on each atom in the molecule. Even though 'real molecules' do not have formal charges, the concept helps in understanding the electron distribution. The sum of formal charges of all atoms must equal the overall charge of the molecule or ion.

Step 6: Verify Lewis Structure

If all previous steps check out, the Lewis structure is probably correct. However, establishing resonance forms (if any exist) is vital to produce an accurate representation of the electron distribution in the molecule.