AQA GCSE Chemistry Chemistry Paper 1 (Foundation), November 2021: Question 3

✅ Correct Answer

2,8,8,1

💡 Key Knowledge

• Shell 1 holds up to 2 electrons.
• Shell 2 holds up to 8 electrons.
• Shell 3 holds up to 8 electrons (for GCSE elements up to Calcium).
• 2 + 8 + 8 = 18 electrons, leaving 1 electron in the 4th shell: total = 19.

✅ Correct Answer

☑ They have the same number of outer shell electrons.

🧠 Exam Technique

The group number on the periodic table tells you the number of electrons in an atom's outermost shell. Chemical reactions depend on losing, gaining, or sharing these valence electrons. Since all Group 1 atoms have 1 outer shell electron, they react in similar ways.

❌ Common Errors

Confusing shells with outer electrons. They do not have the same number of total shells—each step down the group adds a new shell!

✅ Correct Answer

☑ Metallic

❌ Examiner Pitfall

Many students see "sodium" and instantly tick ionic because sodium forms ions in compounds. However, the question asks about sodium on its own (an element). A pure metal atom lattice held together by delocalised electrons has metallic bonding.

✅ Correct Answers (Any two)

• Melts into a ball
• Floats on the water
• Moves (very) quickly / darts on the surface
• Bubbles / effervescence / fizzing (very quickly)
• Also allowed: burns with a yellow/orange flame

🧠 Observation vs Theory

An observation is something you can see, hear, or feel. Never write names of invisible products such as "hydrogen gas is made" or "sodium hydroxide forms". Write what you physically witness: fizzing/bubbles, floating, or melting into a shiny sphere.

✅ Correct Answers

03.5: Reactivity increases down the group. [1 mark]

03.6 (Any two comparative points):

• Speed of movement increases (e.g. moves slowly with Li → moves very quickly with K).
• Rate of bubbling increases (e.g. bubbles slowly with Li → bubbles very quickly with K).
• Lithium does not melt → sodium/potassium melts into a ball.
• No flame produced for Li → flame appears for K → explosion for Rb.

🧠 Exam Technique: Making Comparisons

For question 03.6, you must link the trend to the table data by showing a progression or change. Do not just restate what one metal does in isolation. Mention the contrast or use comparative words like "faster", "more vigorous", or "Li doesn't melt whereas Na and K do".

✅ Correct Answer

☑ Hydrogen

💡 Standard Word Equation

Alkali Metal + Water → Metal Hydroxide + Hydrogen

Example: 2Na + 2H₂O → 2NaOH + H₂

The hydrogen gas catches fire with potassium due to the high heat released!

✅ Mark Scheme Breakdown

• Mark 1: Sodium ion has an electronic structure of 2,8 .
• Mark 2: Fluoride ion has an electronic structure of 2,8 (showing 1 transferred electron).
• Mark 3: Correct charges: + on the sodium ion AND − on the fluoride ion.

❌ Common Errors

• Omitting charges: Forgetting to write the + and − outside the brackets. Both charges are required to secure the 3rd mark!
• Wrong symbol type: Drawing the transferred electron as another cross instead of a dot (or circle), making it impossible to see electron transfer.
• Leaving the 3rd shell: Leaving an electron on sodium's 3rd shell instead of transferring it completely.