Draw Lewis dot structures

Step-by-step guide

STEP 1: Count all valence (outer shell) electrons.

STEP 2: Draw the least electronegative atom in the center and arrange the other atoms around the central atom.

STEP 3: Connect each atom to the central atom with a single bond (one electron pair).

STEP 4: Complete octets with electrons as lone pairs at the terminal atoms first (except for hydrogen). Add remaining atoms (if any) to the central atom.

STEP 5: Complete the central atom’s octet by making multiple bonds with the terminal atoms.

STEP 6 (for some molecules): Depending on which electrons you moved in step 5, a variety of resonance structures can be determined.

Example: CO₂

Let’s see how to apply the five steps to the Lewis structure of carbon dioxide or short CO₂ - a gas that we breathe every day.

STEP 1: The total number of electrons in CO₂ is 4 (C) + 6 (O) + 6 (O) = 16

STEP 2: C is less electronegative than O. So the C needs to be placed in the center surrounded by the oxygen.

STEP 3: Connect the central atom with a single bond. Substract those electrons from the total number of electrons.

STEP 4: Now complete octets with electrons as lone pairs at the terminal atoms first and subtract those electrons from the total number of electrons.

STEP 5: Finally, complete the central atom’s octet by making multiple bonds with the terminal atoms. Lone electron pairs can also be shown as a single line.

STEP 6: This step can be omitted in the case of CO₂, as only one possible Lewis dot structure exists.