2aInorganic Chemistry
Group 1 (alkali metals) – lithium, sodium and potassium — Edexcel Linear - OL (Chemistry) Revision Notes & Topical Questions
10 min read 8 parts Lesson 1 of 23 1 quiz
Curriculum Equation Key معادلة تفاعل تكوين الإستر (الأسترة) - Esterification Reaction EquationFast Exam Solution
R-COOH + R2-OH ⇌ (conc. H₂SO₄) R-COO-R2 + H₂O
Word Equation & Conditions: حمض كربوكسيلي + كحول (في وجود حمض الكبريتيك المركز كعامل حفاز ونازع للماء) ⇌ إستر + ماء
Location & Specifications: الكيمياء العضوية للثانوية العامة والتحصيلي و Edexcel Chemistry.
Lesson summary
Group 1 (alkali metals) Edexcel O Level Linear Chemistry notes: understand how the similarities in the reactions of these elements with water provide evidence for their recognition as a family of elementsTransition metals form coloured ions due to d-electron transitions.Cu²⁺ solu…
- Halogen displacement
- Reactivity increases down Group 1
- Why is it difficult to confirm predictions about francium?
- Lithium reacts with chlorine. What type of compound forms, and why?
- Group 1 (alkali metals) Edexcel O Level Linear Chemistry: what to do next
- Group 1 (alkali metals) Edexcel O Level Linear Chemistry: revision checklist
Part 1 of 7Key ideas
Key ideas
Transition metals form coloured ions due to d-electron transitions.
Cu²⁺ solution is blue; Fe³⁺ is yellow-brown.
Halogen displacement
Cl₂ + 2KBr → 2KCl + Br₂.
One electron in their outer shell
All Group 1 elements have one electron in their outer shell: lithium 2,1; sodium 2,8,1; potassium 2,8,8,1.
Full shell is added
Going down the group, a full shell is added at each step, which is why the elements stay in the same group but react more readily.
Reactivity increases down Group 1
Reactivity increases down Group 1 lithium is the least reactive at the top, sodium and potassium react with increasingly vigorous fizzing, rubidium and caesium react more vigorously still with air and water, and francium is the most reactive.
Potassium
Potassium burns with a lilac flame when it reacts.
Denser than Group 1
The Periodic Table lets you predict boiling point, melting point, density and reactivity,
- and the common trends: Group 1 metals react quickly with water;
- the noble gases are unreactive;
- the transition elements are denser than Group 1;
- Group 7 reactivity decreases down the group;
- Group 1 melting point decreases down the group.
Ionic
Lithium and sodium react with Group 7 elements to form ionic compounds.
Francium
Francium is rare and radioactive, which is why predictions about it are hard to confirm.
Part 2 of 7Syllabus points
Syllabus points
understand how the similarities in the reactions of these elements with water provide evidence for their recognition as a family of elements
understand how the differences between the reactions of these elements with air and water provide evidence for the trend in reactivity in Group 1
use knowledge of trends in Group 1 to predict the properties of other alkali metals 2.4C explain the trend in reactivity in Group 1 in terms of electronic configurations
Part 3 of 7Process & sequence
Flame tests
Li – red
Na – yellow
K – lilac
Ca – brick red
Cu – blue-green
- Group 1 metal
- + water
- → hydroxide
- + hydrogen
Order these metals by how vigorously they react with water, least to most, and use it to answer trend questions.
1
Lithium — relatively slow, fizzing
2
Sodium — more vigorous, dissolves quickly
3
Potassium — most vigorous, lilac flame
4
Rubidium — explodes with sparks
5
Caesium — violent explosion
6
Francium — most reactive, too reactive to predict safely
Explaining the trend from structure
1
Each element has one electron in its outer shell
2
A full shell is added on going down the group
3
The atoms therefore lose that electron more readily
4
Reactivity increases down the group
Part 4 of 7Worked examples
Worked examples
More vigorously than sodium
Potassium is placed below sodium in Group 1. Predict what happens when it is added to water.
- It reacts more vigorously than sodium: fizzing rapidly, moving on the surface, dissolving very quickly and burning with a lilac flame.
- The prediction follows from the trend that reactivity increases down Group 1.
Melting point decreases down Group 1
A table gives the melting points of lithium, sodium and potassium. What does the Periodic Table let you conclude?
- Order the metals by their group position and look for the pattern: the melting point decreases down Group 1.
- The same method works for density and reactivity — position in the Table lets you predict the property.
Why is it difficult to confirm predictions about francium?
- Francium is rare and radioactive, so there is too little of it, and it is hazardous to use, to test the predictions experimentally.
Lithium reacts with chlorine. What type of compound forms, and why?
- An ionic compound: lithium has one outer electron,
- which it transfers to chlorine, a Group 7 element,
- so the two become charged particles held together.
Part 5 of 7Summary
1
Group 1 reactivity increases down the group.
2
Transition metals are good catalysts.
3
Every Group 1 metal has one outer electron, so they react in the same way.
4
Reactivity increases down the group: Li → Na → K → Rb → Cs → Fr.
5
Sodium fizzes and moves rapidly and dissolves; potassium is more vigorous still with a lilac flame.
6
A full shell is added each step down, so the trend can be predicted from position.
7
Group 1 melting point decreases down the group; transition metals are denser.
Part 6 of 7Keep going
Group 1 (alkali metals) Edexcel O Level Linear Chemistry: what to do next
These Group 1 (alkali metals) Edexcel O Level Linear Chemistry notes covered the key ideas, worked examples and exam technique for this topic. Check your Group 1 (alkali metals) Edexcel O Level Linear Chemistry understanding with the practice questions below, then reread any Group 1 (alkali metals) Edexcel O Level Linear Chemistry point you were unsure about before moving on.
Group 1 (alkali metals) Edexcel O Level Linear Chemistry: revision checklist
1
Revise the main Group 1 (alkali metals) Edexcel O Level Linear Chemistry definitions until you can write them from memory.
2
Practise Group 1 (alkali metals) Edexcel O Level Linear Chemistry exam questions under timed conditions.
3
Link each Group 1 (alkali metals) Edexcel O Level Linear Chemistry idea to a diagram or a worked example.
4
List the common Group 1 (alkali metals) Edexcel O Level Linear Chemistry mistakes and how to avoid them.
2
Previous lesson: 1g Covalent bonding — Notes
5
Official syllabus: Pearson Edexcel International GCSEs
Part 7 of 7Compare: Compare
| Group | Elements | Reactivity trend | Typical ion | Property | Use |
|---|---|---|---|---|---|
| 1 Alkali metals | Li, Na, K | Increases down | +1 | React with water → hydroxide + H₂ | Na lamps |
| 2 Alkaline earth | Mg, Ca, Ba | Increases down | +2 | Less reactive than group 1 | Ca in bones |
| Transition metals | Fe, Cu, Zn | Variable | Various | Coloured compounds, catalysts | Fe in Haber |
| 17 Halogens | F, Cl, Br, I | Decreases down | −1 | Displacement reactions | Cl₂ water treatment |
| 18 Noble gases | He, Ne, Ar | Unreactive | None | Full outer shell | Balloons, lighting |
| Metal | Observation |
|---|---|
| Lithium | Relatively slow; fizzing; moves on the surface |
| Sodium | More vigorous fizzing; moves rapidly; dissolves quickly |
| Potassium | Most vigorous of the three; lilac flame; dissolves very quickly |
| Rubidium | Explodes with sparks |
| Caesium | Violent explosion |
| Francium | Too reactive to predict |
Key terms
Command terms
Command terms
Give / State / Name
Recall a fact; one idea per mark.
Define
Give the exact meaning using the specification keywords.
Describe
Give an account of what happens / the pattern in data, quoting values; no reasons needed.
Explain
Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.
Suggest
Use knowledge in a new context; more than one answer may be accepted.
Compare
Similarities and differences; each point must refer to both items.
Calculate
Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.
Discuss
Explore the issue from different angles and link the points.
Evaluate / Assess
Weigh strengths and weaknesses and reach a supported judgement.
Deduce
Draw a conclusion from the information given.
Justify
Support a statement/choice with evidence.
Exam technique
Keywords the mark scheme looks for in this lesson
Keywords the mark scheme looks for in this lesson
Alkali metals · Alkaline earth metals · Halogens · Noble gases · Transition metals · Complex ion · Ligand · Flame test
Learn each definition in the Key words tab exactly; a missing keyword in a definition usually loses the mark.
How to get full marks (examiner guidance)
1
Use specification keywords exactly (e.g. electronegativity, nucleophile, dynamic equilibrium, activation energy).
2Link ideas
Link ideas for “explain” each marking point is usually a cause → consequence step; unlinked facts often score nothing.
3Use the information in the question
“discuss/evaluate” answers must use the data provided and match the number of marks.
4
Convert units carefully (mg → g, cm³ → dm³) and show working for calculations.
5Avoid vague words
“it”, “stuff”, “things”, “goes up”, “energy is made”. Name the substance and the process.
6
Do not extrapolate a graph line beyond the data or to zero unless asked.
7
Six-mark extended responses are marked on content AND a logical, linked line of reasoning.
8Keywords the mark scheme looks for in this lesson
- One electron in the outer shell — Full shell added — Reactivity increases down the group — Fizzing — Moves on the surface — Dissolves — Lilac flame — Melting point decreases — Denser (transition metals) — Ionic
- Describe what you see first (fizzing, movement, dissolving, flame colour), then link it to the trend.
- Observations without the trend earn only the practical marks.
9Prediction questions
- Always give the reason: "reactivity increases down Group 1, so rubidium reacts more vigorously than sodium".
- A prediction with no reason loses the explanation mark.
- Never write "more explosive" as a fact for francium — the board's position is that francium is too reactive to predict and is rare and radioactive.
10Reading data tables
- Order the elements by group position first, then look for the direction of change.
- State both the pattern and what it lets you predict.
Marked practiceQuizzes for this lesson
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