Group 0 and Group 1
SPEC 4.1.2.4–4.1.2.5 • PERIODIC TABLE
The most stable elements vs the most reactive metals. Noble gases, alkali metals, water reactions, the helium exception, and the four-step HT reactivity trend the examiner wants every time.
Group 0 — The Noble Gases
Group 0 sits in the far-right column of the periodic table. Six elements — all gases at room temperature, all unreactive, all very different from anything else in the table.
The Six Noble Gases
He • Ne • Ar • Kr • Xe • Rn
helium, neon, argon, krypton, xenon, radon — in order of increasing atomic number down the group.
Three Defining Properties
Unreactive — they don't easily form compounds or molecules
Monatomic — exist as single atoms (not diatomic like O₂ or N₂)
Boiling points increase down the group (atoms get heavier → stronger intermolecular forces)
Why Are Noble Gases Unreactive?
The defining question on Group 0 — and one with a very specific mark-scheme answer.
Mark-Scheme Answer
Noble gases are unreactive because they have a stable arrangement of electrons in their outer shell — 8 outer electrons, except helium which has 2.
The Helium Exception
Helium has only 2 electrons in total. Both fill its first (and only) shell. The first shell holds a maximum of 2 electrons, so helium is stable with 2, not 8.
Examiner Alert (P1 Jun22 Q05.4)
"All noble gases have 8 outer electrons" loses the mark. The full mark-scheme phrase is: "8 outer (shell) electrons, except helium which has 2". One sentence. One exception. Don't leave it out.
Boiling Points Down Group 0
Boiling points increase as you go down Group 0 — a graph-reading question that appears regularly.
ElementAtomic numberRelative atomic massBoiling point (°C)
He24−269
Ne1020−246
Ar1840−186
Kr3684−153
Xe54131−108
Rn86222−62
The Trend Reason
Going down Group 0, the relative atomic mass increases. Heavier atoms have stronger intermolecular forces, so more energy is needed to separate the atoms — boiling point goes up.
Group 1 — The Alkali Metals
Group 1 is the leftmost column (excluding hydrogen). Six metals — all soft, all reactive, all forming 1+ ions. The complete opposite of Group 0.
The Six Alkali Metals
Li • Na • K • Rb • Cs • Fr
lithium, sodium, potassium, rubidium, caesium, francium.
Why "Alkali"?
When Group 1 metals react with water, they produce a metal hydroxide that dissolves to form an alkaline solution. That's where the group name comes from.
Defining Feature
Every Group 1 element has one electron in its outer shell. That single electron is easily lost → forms a 1+ ion. This is why all Group 1 elements have similar chemistry.
Group 1 Reactions — Three Patterns
Spec content: alkali metals react with oxygen, chlorine, and water. The spec requires you to know the reactions of the first three alkali metals (Li, Na, K) with all three. The equations below show the general pattern — pick any Group 1 metal and the same form of equation works.
With Oxygen → Metal Oxide
4Li + O₂ → 2Li₂OForms a white solid (metal oxide). Sodium and potassium tarnish quickly when cut, exposing the shiny metal underneath only briefly. (Na and K do the same — e.g. 4Na + O₂ → 2Na₂O.)
With Chlorine → Metal Chloride
2Na + Cl₂ → 2NaClForms a white crystalline ionic solid (metal chloride). Same pattern for Li and K (2Li + Cl₂ → 2LiCl; 2K + Cl₂ → 2KCl).
With Water → Metal Hydroxide + Hydrogen
2Na + 2H₂O → 2NaOH + H₂The most-examined reaction. Produces a metal hydroxide (alkaline) and hydrogen gas (squeaky pop with a lit splint). Slide 7 covers Li and K versions of this reaction.
Water Reactions — Li, Na, K
The general equation is the same; the observations get more dramatic going down the group.
Lithium
2Li + 2H₂O → 2LiOH + H₂
Floats; fizzes slowly
Becomes smaller
No flame
Sodium
2Na + 2H₂O → 2NaOH + H₂
Floats; melts to a ball
Moves rapidly across surface
Fizzes vigorously
Potassium
2K + 2H₂O → 2KOH + H₂
Floats; melts
Lilac flame ignites the H₂
Can crackle / explode
General Equation
2M + 2H₂O → 2MOH + H₂
(M = any Group 1 metal). The hydroxide MOH dissolves to give an alkaline solution — that's why these are called the alkali metals.
What Counts as an "Observation"?
An observation is something you can directly see or hear. A deduction is what you conclude from it. Examiners want observations only.
✔ Valid Observations
Effervescence / bubbles / fizzing
(Metal) floats
(Metal) moves around
(Metal) becomes smaller
(Metal) melts
(Metal) forms a ball
Flame
Explosion / crackling sound
✗ Loses the Mark
"Gas produced" — that's a deduction, not an observation
"Fizzing" and "bubbling" listed as two separate observations — they're the same thing
"Hydrogen made" — deduction
"Solution clear" — clear is not a colour. Use "colourless"
Examiner Alert (P1 Jun24 Q02.2)
The mark scheme accepts "effervescence / bubbles / fizzing" as one observation — pick one. "Gas produced" is explicitly not accepted because it's a deduction from seeing bubbles, not the bubbles themselves.
Why the Solution is Alkaline
Once the metal has reacted, the resulting hydroxide dissolves and turns indicators alkaline colours. AQA tests this in two parts: state the colour, then explain why.
Indicator Colours in Alkali (Group 1 + water solution)
Universal indicator: blue / violet / purple
Phenolphthalein: pink
Litmus: blue
Mark-Scheme Reasoning
The solution is alkaline because potassium hydroxide (or sodium hydroxide, etc.) contains hydroxide ions (OH⁻). Hydroxide ions in solution make it alkaline (or "basic" — the mark scheme accepts both).
Examiner Alert (P1 Jun24 Q02.3)
"Potassium is an alkali" loses the mark. Potassium is a metal. The potassium hydroxide solution is alkaline because it contains OH⁻ ions. Always identify the specific alkaline species, not just the metal.
Reactivity Increases Down Group 1
One of the most-examined trends in Module 1. Going down the group, each metal reacts more vigorously with water than the one above it.
Less Reactive (top of group)
Li → Na → K → Rb → Cs
More Reactive (bottom of group)
(reactivity increases down the group)
The Key Comparison
Lithium fizzes slowly on water. Sodium melts and shoots across the surface. Potassium ignites and burns with a lilac flame. By caesium, the reaction is dangerously explosive. Same general reaction, just more vigorous each time.
Compare with Group 7 (Lesson 1.08)
Group 7 (halogens) shows the opposite trend — reactivity decreases down the group. The mechanisms are mirror images: Group 1 loses electrons more easily down the group; Group 7 gains electrons less easily down the group.
The 4-Mark Reactivity Chain HT only
For Higher Tier, the explanation has four required steps. Each step earns one mark. Drop any of them and you lose marks.
1More shells. Going down Group 1, each atom has one more occupied electron shell.
2Outer electron further from the nucleus, and more shielded by inner-shell electrons.
3Weaker (electrostatic) attraction between the positive nucleus and the negative outer electron.
4Less energy needed to lose the outer electron → metal reacts more easily / more vigorously.
Memory Hook
Shells → Distance + Shielding → Weaker Attraction → Easier to Lose. Four links. Four marks.
Examiner Alert — The Reactivity Trap
Examiner Alert (P1 Jun22 Q05.2 / P1 Jun23 Q09.5)
Saying only "the outer electron is further from the nucleus" is not enough. The mark scheme requires three things together: (a) the force is attraction, (b) it acts between the nucleus and the outer electron, (c) the weaker attraction means the electron is lost more easily.
✗ Loses Mark
"The outer electron is further from the nucleus, so reactivity increases."
Distance stated, but no mention of attraction, why it matters, or how it links to losing the electron.
✔ Fixes the Trap
"The outer electron is further from the nucleus, so the electrostatic attraction between the nucleus and the outer electron is weaker, and less energy is needed to lose the electron."
Adds the three required pieces: attraction · weaker · electron lost more easily. (Combine with "more shells / more shielded" for full 4 marks — see Slide 11.)
Wrong Force Names
Magnetic attraction and intermolecular attraction are both wrong. The force is electrostatic — between the positive nucleus and the negative outer electron.
Group 0 vs Group 1 — Side by Side
The contrast between these two groups is the central concept of Module 1. AQA tests both individually, and sometimes asks you to explain the difference.
FeatureGroup 0 (Noble Gases)Group 1 (Alkali Metals)
Outer electrons8 (He = 2)1
StabilityAlready stableUnstable — needs to lose 1e⁻
ReactivityUnreactiveVery reactive (more vigorous down the group)
FormMonatomic gasesSoft solid metals
Ion formedNone (no compounds)1+ (M⁺)
Trend down groupBoiling points increaseReactivity increases
Practice Question 1
two
2 MARKS
Source: P1 Jun24 Q02.2
P
Any two of: effervescence / bubbles / fizzing; potassium floats; potassium moves around; potassium becomes smaller; potassium melts; flame; explosion. Mark scheme also accepts "potassium forms a ball". [1 mark each]
E
Example pair: "(1) Potassium floats on the water and moves around. (2) The potassium melts and a flame is produced." Two distinct observations, both directly visible. [2 marks]
E
Don't write: "Gas produced" (a deduction, not an observation); "fizzing AND bubbling" (one observation listed twice — same thing); "hydrogen made" (deduction). Note: mark scheme says "ignore colour of flame" — writing "lilac flame" is fine but the colour itself doesn't add a mark.
Practice Question 2
one
2 MARKS
Source: P1 Jun24 Q02.3
P
Colour: blue / violet / purple. [1 mark]
E
Reason: The (potassium hydroxide) solution is alkaline — mark scheme also accepts "contains OH⁻ / hydroxide ions" or "is basic". [1 mark]
E
Don't write: "Potassium is an alkali" (potassium is a metal — it's the hydroxide solution that's alkaline). Don't write "green" (neutral) or "red/orange" (acidic) — both lose the mark.
Practice Question 3 HT only
4 MARKS
Pattern: P1 Jun22 Q05.2 / P1 Jun23 Q09.5
1
Going down Group 1, each atom has more (occupied) electron shells. [1 mark]
2
The outer electron is further from the nucleus and more shielded by inner electrons. [1 mark]
3
The (electrostatic) force of attraction between the nucleus and the outer electron is weaker. [1 mark]
4
So less energy is needed to lose the outer electron → the metal is more reactive. [1 mark]
P
Why all 4 are needed: "Electron is further away" alone is the cause but doesn't explain why distance matters or what changes. The mark scheme requires the full mechanistic chain: more shells → distance + shielding → weaker attraction → easier to lose.
Common Errors — Quick Check
The phrases on the left turn up every year and lose marks. The right column is what the mark scheme actually accepts.
Loses the markWins the mark
"All noble gases have 8 outer electrons""8 outer electrons, except helium which has 2 "
"Gas produced""Effervescence" / "bubbles" / "fizzing" (one of these)
"Fizzing and bubbling" (counted as two)Pick one — they're the same observation
"Potassium is an alkali""Potassium hydroxide solution is alkaline / contains OH⁻ ions"
"Clear solution"" Colourless solution"
"Outer electron is further away" (alone)"Weaker electrostatic attraction between nucleus and outer electron → lost more easily"
"Magnetic / intermolecular attraction"" Electrostatic attraction"
Summary
Group 0 — Noble Gases (4.1.2.4)
He, Ne, Ar, Kr, Xe, Rn
Unreactive — stable arrangement of electrons in outer shell
8 outer electrons, except helium which has 2
Monatomic; boiling points increase down the group
Group 1 — Alkali Metals (4.1.2.5)
Li, Na, K, Rb, Cs, Fr — all have 1 outer electron → form 1+ ions
With water: 2M + 2H₂O → 2MOH + H₂ — alkaline solution + hydrogen gas
Solution alkaline because metal hydroxide releases OH⁻ ions
Reactivity increases down the group : Li < Na < K < Rb < Cs
HT Reactivity Trend — 4 marks
(1) More electron shells
(2) Outer electron further away + more shielded
(3) Weaker electrostatic attraction (nucleus ↔ outer electron)
(4) Less energy to lose outer electron → more reactive
Top Exam Tip
Three "every year" traps: (1) helium exception when discussing Group 0; (2) "hydroxide solution" not "metal is an alkali"; (3) full 4-step electrostatic chain for HT reactivity. Memorise them as one-liners — examiners use the same wording every paper.
Next: Group 0 — The Noble Gases