Ionic bonding revision: Exam practice questions on how sodium and chlorine atoms react to form sodium chloride.

Let's go through each question in the worksheet and solve them step by step.

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Question 1: Use the diagrams to describe how sodium and chlorine atoms react to form sodium chloride. (6 marks)

Answer:

Sodium (Na) is a metal with one electron in its outer shell, while chlorine (Cl) is a non-metal with seven electrons in its outer shell. To achieve a stable electron configuration (like a noble gas), sodium loses one electron to form a sodium ion (Na⁺), and chlorine gains that electron to form a chloride ion (Cl⁻).

This transfer of an electron from sodium to chlorine results in the formation of oppositely charged ions. The electrostatic attraction between the positively charged Na⁺ ion and the negatively charged Cl⁻ ion forms an ionic bond, creating the ionic compound sodium chloride (NaCl).

The diagram shows:
- Sodium atom (Na) with 11 protons and 11 electrons, having 1 valence electron.
- Chlorine atom (Cl) with 17 protons and 17 electrons, having 7 valence electrons.
- After electron transfer:
- Sodium becomes Na⁺ (loses 1 electron → now has 10 electrons).
- Chlorine becomes Cl⁻ (gains 1 electron → now has 18 electrons).
- The resulting ions are held together by strong electrostatic forces — this is the ionic bond.

✔ This process is called ionic bonding and occurs due to the transfer of electrons from a metal to a non-metal.

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Question 2: Complete the table using the charges on the ions to deduce the formula of each ionic compound. (5 marks)

We need to balance the charges so that the total positive charge equals the total negative charge.

| Metal | Charge on metal ion | Non-metal | Charge on non-metal ion | Name of ionic compound | Formula of ionic compound |
|-------------|---------------------|-----------|--------------------------|----------------------------|----------------------------|
| Calcium | 2+ | Bromine | 1- | Calcium bromide | CaBr₂ |
| Magnesium | 2+ | Sulfur | 2- | Magnesium sulfide | MgS |
| Lithium | 1+ | Oxygen | 2- | Lithium oxide | Li₂O |
| Potassium | 1+ | Iodine | 1- | Potassium iodide | KI |
| Magnesium | 2+ | Chlorine | 1- | Magnesium chloride | MgCl₂ |

#### Explanation for each row:

1. Calcium bromide
- Ca²⁺ and Br⁻
- Need two Br⁻ to balance one Ca²⁺ → CaBr₂

2. Magnesium sulfide
- Mg²⁺ and S²⁻
- Charges balance directly → MgS

3. Lithium oxide
- Li⁺ and O²⁻
- Need two Li⁺ to balance one O²⁻ → Li₂O

4. Potassium iodide
- K⁺ and I⁻
- Charges balance directly → KI

5. Magnesium chloride
- Mg²⁺ and Cl⁻
- Need two Cl⁻ to balance one Mg²⁺ → MgCl₂

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✔ Final Answer Table:

| Metal | Charge on metal ion | Non-metal | Charge on non-metal ion | Name of ionic compound | Formula of ionic compound |
|-------------|---------------------|-----------|--------------------------|----------------------------|----------------------------|
| Calcium | 2+ | Bromine | 1- | Calcium bromide | CaBr₂ |
| Magnesium | 2+ | Sulfur | 2- | Magnesium sulfide | MgS |
| Lithium | 1+ | Oxygen | 2- | Lithium oxide | Li₂O |
| Potassium | 1+ | Iodine | 1- | Potassium iodide | KI |
| Magnesium | 2+ | Chlorine | 1- | Magnesium chloride | MgCl₂ |

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Summary:

- Ionic bonding involves electron transfer from metal to non-metal, forming ions that attract each other.
- The formula of an ionic compound is determined by balancing the charges of the ions involved.

Let me know if you'd like a visual explanation or further practice!