Explaining the increase in reactivity
3 marks · Easy| Metal | Number of electron shells | Relative reaction speed |
|---|---|---|
| Lithium | 2 | slow |
| Sodium | 3 | medium |
| Potassium | 4 | fast |
State the trend in reactivity as you go down Group 1 based on this table.
Describe how the number of electron shells changes across the metals in the table.
Explain, using the data, why potassium reacts faster than sodium.
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Show answer
(a) Reactivity increases down Group 1.
(b) The number of electron shells increases from lithium to potassium.
(c) Potassium has more electron shells, so its outer electron is further from the nucleus and lost more easily.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Identifies that reactivity increases down Group 1.
B2 (b) · 1 mark · States that the number of shells increases from lithium to potassium.
M1 (c) · 1 mark · Explains that potassium's outer electron is further from the nucleus and lost more easily.
Worked solution
a) Reactivity increases down the group.
b) The number of electron shells increases from 2 in lithium to 4 in potassium.
c) Potassium's outer electron is in the 4th shell so is further from the nucleus and lost more easily.