Year 9 Science · Unit 2 · Lesson 06
Apply Worksheet
Learning Goals
Compare two
Complete the table to compare sodium (Na, Z=11) and chlorine (Cl, Z=17). Use your knowledge of electron shells and stability.
| Feature | Sodium (Na) | Chlorine (Cl) |
|---|---|---|
| Electron configuration | ||
| Number of outer shell (valence) electrons | ||
| Electrons needed to fill the outer shell | ||
| Electrons to lose to reach a full inner shell | ||
| Type of ion formed when reacting (e.g. Na⁺ or Cl⁻) |
Scenario
Magnesium (Mg, Z=12) and oxygen (O, Z=8) react together in a bright white flash of light to form magnesium oxide (MgO). This reaction is so energetic it is used in fireworks and road flares, once ignited, magnesium cannot be extinguished with water. The product, MgO, is used to line furnaces that must withstand temperatures above 2800 °C.
(a) Write the electron configurations of magnesium (Mg, Z=12) and oxygen (O, Z=8).
(b) Predict how many electrons magnesium will lose and how many electrons oxygen will gain when they react. Show your reasoning by referring to each atom's electron configuration.
(c) Justify why the resulting compound MgO is extremely stable. Use the idea of full outer shells in your answer.
1. Fluorine (F, Z=9) is described as the most reactive non-metal on Earth. Using its electron configuration, explain why fluorine is so reactive and what type of ion it forms.
2. Potassium (K, Z=19, configuration 2,8,8,1) is more reactive than sodium (Na, Z=11, configuration 2,8,1), even though both have 1 valence electron. Using what you know about electron shells and stability, suggest a reason why potassium is more reactive.
Wrap Up
In one sentence, what was the main idea of this lesson?