Year 9 Science · Unit 2 · Lesson 06
Apply Worksheet
Learning Goals
1. What is a valence electron, and why are valence electrons the ones that matter in chemical reactions?
Compare two
Complete the table for sodium (atomic number 11) and chlorine (atomic number 17).
| Feature | Sodium (Na) | Chlorine (Cl) |
|---|---|---|
| Electron configuration | ||
| Number of valence electrons | ||
| Easier to lose or to gain electrons? How many? | ||
| Group and period |
Scenario: a magnesium flare
Magnesium (atomic number 12) burns in oxygen (atomic number 8) with a dazzling white light, so it is used in some fireworks and signal flares. Burning magnesium cannot be put out with water. The product is a white powder, magnesium oxide.
2. Write the electron configurations of magnesium and oxygen.
3. Predict how many electrons each magnesium atom will lose and each oxygen atom will gain when they react. Explain each prediction using the configuration.
Read the data
| Atomic no. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Valence e− | 1 | 2 | 1 | 2 | 3 | 4 | 5 | 7 | 8 |
| Atomic no. | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
|---|---|---|---|---|---|---|---|---|---|---|
| Valence e− | 1 | 2 | 4 | 5 | 7 | 8 | 2 |
Source: electron configurations of elements 1 to 20. The empty boxes are for you to fill in.
4. Fill in the four missing values in Table 1.
5. Describe the repeating pattern in Table 1. Name the three elements where each row of the periodic table ends, and explain why lithium (3), sodium (11) and potassium (19) behave in similar ways.
6. Write the electron configurations of fluorine (9), neon (10) and sodium (11). Compare their valence-electron arrangements to describe the bonding each is likely to form under ordinary conditions. Then explain why those arrangements alone cannot tell you how quickly sodium reacts with water.