AQA GCSE Chemistry Chemistry Paper 1 (Foundation), June 2022: Question 9

✅ Correct Answer

Tick box D

💡 Key Knowledge

• Dull appearance, low melting point (44 °C), and electrical insulator are classic physical properties of non-metals.
• In the periodic table outline, section D represents the non-metals (top-right, above the staircase).

🧠 Exam Technique

Scan the properties first: low melting point + non-conductor = definitely a non-metal. Eliminate sections A, B, and C immediately, as all are metallic.

❌ Common Errors

Confusing section C (metals below the staircase/post-transition metals) with non-metals, or confusing low melting point with Group 1 metals (Group 1 metals conduct electricity!).

✅ Correct Answer

Tick box B

💡 Key Knowledge

• Elements that form ions with different charges (such as R²⁺ and R³⁺) are transition metals.
• For example, iron forms Fe²⁺ and Fe³⁺.
• Section B is the central d-block representing the transition elements.

❌ Common Errors

Selecting A (Group 1 and 2 metals only form 1+ or 2+ ions respectively; they do not form multiple stable oxidation states).

✅ Correct Answers (Any two)

Group 1 elements compared to transition elements:

• Have lower melting / boiling points
• Have lower densities
• Are less strong / weaker
• Are softer (can be cut with a knife)

(Converse statements about transition elements are fully acceptable, e.g. "Transition elements have higher melting points and higher densities.")

💡 Allowed Equivalents

• Allow: Group 1 are more malleable / ductile.
• Allow: Group 1 are not useful as catalysts (transition elements act as catalysts).

❌ Common Errors & Examiner Traps

• Giving chemical properties instead of physical: Mentioning reactivity, reaction with water, or forming coloured compounds gets 0 marks. The question explicitly asked for physical properties.
• Writing "ions have different charges" — this is a chemical property, so it is ignored.
• Vague words: Avoid just saying "density" or "melting point" without stating higher or lower.

🧠 Exam Technique

Always format comparison answers with clear comparative terms: "Group 1 metals have lower melting points" and "Group 1 metals have lower densities". Never state an isolated feature like "they melt".

✅ Correct Answer

Aluminium (atomic number 13) has the configuration 2, 8, 3:

• Innermost shell: 2 electrons
• Second shell: 8 electrons
• Outer shell: 3 electrons

Accepted symbols: crosses (×), dots (•), circles (o), or e⁻.

💡 Examiner-Style Diagram Guidance

When drawing Figure 16:

• Place 2 electrons paired on the 1st ring.
• Place 8 electrons (paired as 4 pairs) evenly on the 2nd ring.
• Place 3 electrons separated or as a pair + single on the 3rd (outer) ring.
• Total = exactly 13 electrons.

❌ Common Errors

• Using the mass number (27) instead of the atomic number (13).
• Miscounting electrons on the middle ring (putting 6 or 7 instead of 8).
• Drawing the electronic structure of the aluminium ion (2, 8) instead of the atom (2, 8, 3).

✅ Correct Model Answer (3 Marking Points)

1. Metals contain delocalised electrons (or "free electrons"). [1 mark]
2. These electrons carry (electrical) charge. [1 mark]
3. The electrons move through the metal / structure. [1 mark]

💡 Metallic Structure Key Concept

Metals consist of a giant lattice of positive metal ions surrounded by a "sea" of delocalised outer-shell electrons that are free to drift through the whole metallic lattice when a potential difference is applied.

❌ Common Errors & Examiner Traps

• "Carry current" / "carry electricity": The mark scheme strictly states: ignore current / electricity for charge. You must state they carry (electrical) charge.
• Saying "positive ions move" — metal ions are fixed in lattice positions and only vibrate; they do not move to conduct electricity.
• Saying electrons move "throughout" instead of "through the structure".

🧠 Exam Technique

Memorise the standard 3-part sentence for electrical conductivity in metals:
"Delocalised electrons [1] are free to move through the structure [1] and carry electrical charge [1]."

✅ Correct Answer

Ionic (bonding)

💡 The Three Bonding Types

• Metal + Non-metal: Ionic bonding (electron transfer)
• Non-metal + Non-metal: Covalent bonding (electron sharing)
• Metal + Metal: Metallic bonding (delocalised electrons)

✅ Mark Scheme Breakdown (4 Marks)

• Mark 1: Magnesium (atom) loses electrons.
• Mark 2: Oxygen (atom) gains electrons.
• Mark 3: Exactly two electrons are transferred.
• Mark 4: Magnesium ions (Mg²⁺) and oxide ions (O²⁻) are formed.

🧠 Top-Level Response Structure

Write your answer in concise bullet points covering all four parts:

• "Magnesium atoms lose electrons"
• "Oxygen atoms gain electrons"
• "Two electrons are transferred from magnesium to oxygen"
• "Forming Mg²⁺ (magnesium) ions and O²⁻ (oxide) ions"

💡 Alternative Acceptable Answers for Mark 4

• "Magnesium forms positive ions and oxygen forms negative ions"
• "Both form a complete / full outer shell (of electrons)"
• Formulae: Mg²⁺ and O²⁻

❌ Common Errors

• Describing sharing of electrons (confusing ionic with covalent bonding) — loses marks.
• Saying "1 electron is transferred" instead of 2.
• Referring to "oxygen ions" instead of "oxide ions" (though naming the charges Mg²⁺ and O²⁻ guarantees the mark).
• Omitting the word "ions" when describing the products.