Question

(d) complete the dot - and - cross diagram to show the arrangement of electrons in a molecule of carboxylic acid y.

Explanation:

Step1: Recall carbon - electron configuration

Carbon has 4 outer - shell electrons. In a carboxylic acid, it forms bonds to achieve an octet. It has a double bond to one oxygen and single bonds to another oxygen and a hydrogen (or an alkyl group).

Step2: Recall oxygen - electron configuration

Oxygen has 6 outer - shell electrons. The oxygen in the C=O double bond shares 2 electrons with carbon and has 2 lone pairs. The other oxygen in the C - O bond shares 1 electron with carbon, 1 with hydrogen, and has 2 lone pairs.

Step3: Recall hydrogen - electron configuration

Hydrogen has 1 outer - shell electron. It shares this electron with oxygen or carbon to achieve a duet.
For the given carboxylic acid structure:

• The carbon in the middle should have 4 dots around it to represent its own electrons. It forms a double bond with the top - oxygen. So, the top - oxygen should have 2 crosses from the carbon (in the double bond), and 4 more electrons (2 lone pairs) shown as dots or crosses (let's say dots).
• The carbon also forms a single bond with the right - oxygen. The right - oxygen should have 1 cross from the carbon, 1 cross from the hydrogen, and 4 more electrons (2 lone pairs) shown as dots.
• The hydrogen atoms each have 1 cross from the atom they are bonded to (either carbon or oxygen).

Answer:

Draw the following:

• On the central carbon, add 4 dots around it.
• On the top - oxygen, add 2 crosses from the carbon (in the double bond) and 4 dots (2 lone pairs).
• On the right - oxygen, add 1 cross from the carbon, 1 cross from the hydrogen, and 4 dots (2 lone pairs).
• On each hydrogen, add 1 cross from the atom it is bonded to.