Describe Group I trends and predict reactions using evidence.
| English | Chinese |
|---|---|
| alkali metal | 碱金属 |
| density | 密度 |
| reactivity | 反应活泼性 |
Try each question before opening its hint or answer. Use paper for calculations and diagrams.
Which reacts more vigorously with water, lithium or potassium? Explain using electron loss.
Locate the two metals in the group and identify the direction of comparison.
Potassium. Its outer electron is farther from the nucleus and more shielded, so it is easier to lose.
Write a balanced equation for potassium reacting with water.
The products are an alkali and hydrogen.
2K + 2H₂O → 2KOH + H₂
Densities: Na 0.97 and K 0.86 g cm⁻³. Use these data to evaluate the claim that density always increases down Group I.
Compare the two numerical densities rather than assuming a trend.
The general trend is increasing density, but K is 0.86 g cm⁻³ and Na is 0.97 g cm⁻³.
Use Lesson 2 in your worksheet for written practice. Your teacher will discuss those answers in class.