Electron Dot Structure of Ethanoic Acid (Acetic Acid)

Before drawing the dots, you must know how many outermost (valence) electrons each atom brings to the table:

• Carbon (C): Atomic number 6. Configuration (2, 4). Needs 4 electrons to complete its octet. (Total 2 Carbon atoms).
• Oxygen (O): Atomic number 8. Configuration (2, 6). Needs 2 electrons to complete its octet. (Total 2 Oxygen atoms).
• Hydrogen (H): Atomic number 1. Configuration (1). Needs 1 electron to complete its duplet. (Total 4 Hydrogen atoms).

The structure is divided into two parts: the Methyl group (CH₃) and the Carboxylic Acid group (COOH).

Step 1: The Methyl Group (CH₃-)

• Take the first Carbon. Draw 4 dots around it.
• Attach 3 Hydrogens to it. Each Hydrogen shares 1 dot with the Carbon, creating three single covalent bonds (C-H).

Step 2: Connecting the Carbons

• Connect the first Carbon to the second Carbon by sharing exactly 1 pair of electrons (a C-C single bond).

Step 3: The Double Bonded Oxygen (=O)

• Take the second Carbon. Attach one Oxygen atom to the top.
• Because Oxygen needs 2 electrons, the Carbon and Oxygen share 2 pairs of electrons (4 dots total) between them. This forms a Double Covalent Bond (C=O).
• Crucial: Do not forget to draw the remaining 4 unused electrons (2 lone pairs) sitting harmlessly on the top Oxygen.

Step 4: The Hydroxyl Group (-OH)

• Attach the second Oxygen to the side of the second Carbon by sharing 1 pair (C-O single bond).
• Finally, attach the last Hydrogen to this Oxygen by sharing 1 pair (O-H single bond).
• Draw the remaining 4 unused electrons (2 lone pairs) on this second Oxygen.

To check your drawing, count the circles. Every Hydrogen circle should contain exactly 2 electrons. Every Carbon and Oxygen circle should contain exactly 8 electrons. The entire molecule is held together by covalent bonding.