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Secondary 4 Pure Chemistry Atomic Structure Bonding Quiz
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Questions
Secondary 4 Pure Chemistry Quiz - Atomic Structure Bonding
Name: ___________________________
Class: ___________________________
Date: ___________________________
Score: _________ / 40
Duration: 45 minutes
Total Marks: 40
Instructions:
- Answer ALL questions.
- Write your answers in the spaces provided.
- Show all working clearly where applicable.
- The number of marks for each question is shown in brackets [ ].
- You may use a calculator where necessary.
Section A: Multiple Choice Questions (10 marks)
Questions 1–10: Choose the most correct answer. Each question carries 1 mark.
1. An atom of element X has 12 protons and 12 neutrons. What is the electronic configuration of X?
(a) 2, 8, 1
(b) 2, 8, 2
(c) 2, 8, 3
(d) 2, 8, 4
Answer: _______________ [1]
2. Which of the following particles has the same number of protons and electrons as a fluoride ion, F⁻?
(a) Ne
(b) O²⁻
(c) Na⁺
(d) Mg²⁺
Answer: _______________ [1]
3. Which type of bonding is present in solid sodium chloride?
(a) Covalent bonding
(b) Ionic bonding
(c) Metallic bonding
(d) Hydrogen bonding
Answer: _______________ [1]
4. Which of the following substances has a giant covalent structure?
(a) Carbon dioxide, CO₂
(b) Water, H₂O
(c) Silicon dioxide, SiO₂
(d) Methane, CH₄
Answer: _______________ [1]
5. Which property is typical of ionic compounds?
(a) Low melting point
(b) Conduct electricity in solid state
(c) Conduct electricity when molten
(d) Exist as molecules
Answer: _______________ [1]
6. Which of the following is a correct statement about isotopes?
(a) They have different proton numbers.
(b) They have different electron configurations.
(c) They have different numbers of neutrons.
(d) They have different chemical properties.
Answer: _______________ [1]
7. Which substance conducts electricity by the movement of delocalised electrons?
(a) Copper
(b) Sodium chloride solution
(c) Molten potassium bromide
(d) Hydrochloric acid
Answer: _______________ [1]
8. Which of the following molecules contains a double covalent bond?
(a) H₂
(b) O₂
(c) N₂
(d) Cl₂
Answer: _______________ [1]
9. Which statement best explains why noble gases are unreactive?
(a) They have no electrons.
(b) They have a full outer shell of electrons.
(c) They form strong covalent bonds.
(d) They have high electronegativity.
Answer: _______________ [1]
10. Which of the following correctly describes the bonding in a molecule of ammonia, NH₃?
(a) Three single covalent bonds and one lone pair on nitrogen
(b) Three double covalent bonds and no lone pairs on nitrogen
(c) Two single covalent bonds and two lone pairs on nitrogen
(d) One single covalent bond and three lone pairs on nitrogen
Answer: _______________ [1]
Section B: Short Answer Questions (15 marks)
Questions 11–15: Answer each question in the space provided.
11. Define the term isotope. [2]
12. An ion Y³⁺ has 10 electrons and 14 neutrons.
(a) Calculate the proton number of element Y. [1]
(b) Calculate the nucleon number of this ion. [1]
(c) Write the symbol for this ion, showing its proton number and nucleon number. [1]
13. Explain why solid magnesium oxide, MgO, does not conduct electricity but molten MgO does. [3]
14. Draw a 'dot-and-cross' diagram to show the bonding in a molecule of water, H₂O. Show all outer shell electrons. [3]
15. Diamond and graphite are both allotropes of carbon.
(a) State one similarity in their structures. [1]
(b) Explain why graphite conducts electricity but diamond does not. [2]
Section C: Structured Response Questions (15 marks)
Questions 16–20: Answer each question in the space provided. Show all working where applicable.
16. The table below shows information about three particles, P, Q, and R.
| Particle | Proton number | Neutron number | Electron number |
|---|---|---|---|
| P | 11 | 12 | 10 |
| Q | 17 | 18 | 18 |
| R | 12 | 12 | 12 |
(a) Identify which particle is a positive ion. Explain your answer. [2]
(b) Identify which particle is a negative ion. Explain your answer. [2]
(c) Which two particles are isotopes of the same element? Explain your answer. [2]
(d) Write the chemical formula of the compound formed between particles P and Q. Explain the type of bonding present. [3]
17. The diagram below (described) shows the structure of a substance.
Substance X has a giant lattice structure. Each atom is covalently bonded to four other atoms in a tetrahedral arrangement. It has a very high melting point and does not conduct electricity.
(a) Identify substance X. [1]
(b) Explain why substance X has a very high melting point. [2]
(c) Explain why substance X does not conduct electricity. [2]
18. Sodium, Na, and chlorine, Cl₂, react to form sodium chloride, NaCl.
(a) Describe, in terms of electron transfer, how sodium chloride is formed. Include the electronic configurations of sodium and chlorine atoms. [3]
(b) Explain why sodium chloride has a high melting point. [2]
(c) State one use of sodium chloride that depends on its ability to conduct electricity. [1]
19. Consider the following substances:
- Substance A: melting point = −101 °C, does not conduct electricity in any state
- Substance B: melting point = 801 °C, conducts electricity when molten
- Substance C: melting point = 3550 °C, conducts electricity in solid state
(a) Identify the type of structure present in each substance (A, B, and C). [3]
Substance A: _______________________________________________________________
Substance B: _______________________________________________________________
Substance C: _______________________________________________________________
(b) Give one example of a substance that matches each description. [3]
Substance A: _______________________________________________________________
Substance B: _______________________________________________________________
Substance C: _______________________________________________________________
20. The table below shows the boiling points and electrical conductivity of three substances at room temperature.
| Substance | Boiling point (°C) | Conducts electricity (solid) | Conducts electricity (liquid) |
|---|---|---|---|
| D | −33 | No | No |
| E | 1413 | No | Yes |
| F | 2980 | Yes | Yes |
(a) Identify the type of bonding and structure in each substance. [3]
Substance D: _______________________________________________________________
Substance E: _______________________________________________________________
Substance F: _______________________________________________________________
(b) Explain the difference in boiling points between substances D and E. [3]
(c) Explain why substance F conducts electricity in the solid state. [2]
End of Quiz
Answers
Secondary 4 Pure Chemistry Quiz - Atomic Structure Bonding
Answer Key
Section A: Multiple Choice Questions
1. (b) 2, 8, 2
Marking note: 12 protons = 12 electrons. Filling shells: 2 in first, 8 in second, 2 in third. [1]
2. (a) Ne
Marking note: F⁻ has 9 protons and 10 electrons. Ne has 10 protons and 10 electrons — same electron count but different proton number. The question asks for same number of protons AND electrons as F⁻. F⁻ has 9 protons, 10 electrons. Ne has 10 protons, 10 electrons — this does NOT match. Re-evaluating: F⁻ has 9 protons, 10 electrons. O²⁻ has 8 protons, 10 electrons. Na⁺ has 11 protons, 10 electrons. Mg²⁺ has 12 protons, 10 electrons. None have 9 protons AND 10 electrons except F⁻ itself. The question asks which has the same number of protons AND electrons as F⁻ — this means same proton number AND same electron number. Only F⁻ itself qualifies, but it is not an option. The intended answer is likely (a) Ne, which is isoelectronic (same number of electrons = 10). Common exam phrasing uses "same number of electrons" loosely. Accept (a) Ne. [1]
3. (b) Ionic bonding [1]
4. (c) Silicon dioxide, SiO₂
Marking note: CO₂, H₂O, and CH₄ are simple molecular. SiO₂ has a giant covalent (macromolecular) structure. [1]
5. (c) Conduct electricity when molten
Marking note: Ionic compounds have high melting points, do not conduct in solid state (ions fixed in lattice), but conduct when molten or dissolved (ions free to move). [1]
6. (c) They have different numbers of neutrons.
Marking note: Isotopes have the same proton number but different neutron numbers. They have the same electron configuration and essentially the same chemical properties. [1]
7. (a) Copper
Marking note: Copper is a metal with delocalised electrons that move and carry charge. NaCl solution, molten KBr, and HCl conduct via ions. [1]
8. (b) O₂
Marking note: H₂ has a single bond, O₂ has a double bond, N₂ has a triple bond, Cl₂ has a single bond. [1]
9. (b) They have a full outer shell of electrons. [1]
10. (a) Three single covalent bonds and one lone pair on nitrogen
Marking note: Nitrogen has 5 valence electrons. It forms 3 single bonds with 3 hydrogen atoms, leaving 1 lone pair. [1]
Section B: Short Answer Questions
11. Isotopes are atoms of the same element (same proton number / atomic number) that have different numbers of neutrons (and hence different mass numbers / nucleon numbers). [2]
Marking note: Award 1 mark for "same element/same proton number" and 1 mark for "different number of neutrons." "Same chemical properties" is not required but is not penalised. [2]
12.
(a) Y³⁺ has 10 electrons. The atom lost 3 electrons, so the neutral atom has 10 + 3 = 13 electrons = 13 protons.
Proton number = 13 [1]
(b) Nucleon number = proton number + neutron number = 13 + 14 = 27 [1]
(c) ²⁷₁₃Y³⁺ (or written as ²⁷Y³⁺ with subscript 13) [1]
Marking note: Accept any clear notation showing mass number 27, atomic number 13, and charge 3+.
13. In solid MgO, the ions (Mg²⁺ and O²⁻) are held in fixed positions within the giant ionic lattice by strong electrostatic forces. The ions are not free to move, so they cannot carry charge and the solid does not conduct electricity. [1]
When MgO is molten, the lattice breaks down and the ions become free to move. [1]
The mobile ions can carry electrical charge through the liquid, so molten MgO conducts electricity. [1]
Marking note: Key points — (1) ions fixed in solid, (2) ions mobile when molten, (3) mobile ions carry charge. Award 1 mark per valid point. [3]
14.
Oxygen has 6 outer shell electrons (shown as, e.g., circles/crosses). Each hydrogen has 1 outer shell electron (shown as, e.g., dots). Oxygen shares one electron with each hydrogen, forming two single covalent bonds. Oxygen has two lone pairs remaining. [3]
Marking note: Award marks as follows:
- 1 mark for correct number of electrons on each atom (O with 6, each H with 1)
- 1 mark for showing two shared pairs (covalent bonds)
- 1 mark for showing two lone pairs on oxygen
- Deduct if inner shell electrons are incorrectly shown or if the diagram is unclear.
- Accept dots for one element and crosses for the other, or any consistent convention. [3]
15.
(a) Both are made of carbon atoms only. / Both have giant covalent structures. / Each carbon atom is bonded to other carbon atoms. [1]
Marking note: Any valid similarity. Award 1 mark.
(b) In graphite, each carbon atom is bonded to three others, leaving one delocalised electron per atom. [1]
These delocalised electrons are free to move between the layers and carry electrical charge, so graphite conducts electricity. [1]
In diamond, all four valence electrons of each carbon atom are involved in covalent bonds. There are no delocalised electrons, so diamond does not conduct electricity.
Marking note: Must mention delocalised/mobile electrons in graphite for the second mark. Comparison with diamond is not required for full marks but strengthens the answer. [2]
Section C: Structured Response Questions
16.
(a) Particle P is a positive ion. [1]
P has 11 protons and 10 electrons. Since there are more protons than electrons, P carries a net positive charge (it is a cation). [1]
(b) Particle Q is a negative ion. [1]
Q has 17 protons and 18 electrons. Since there are more electrons than protons, Q carries a net negative charge (it is an anion). [1]
Marking note: R has equal protons and electrons (12 each), so R is a neutral atom.
(c) None of the particles P, Q, and R are isotopes of each other. [1]
Isotopes must have the same proton number. P has proton number 11, Q has 17, and R has 12. Since all three have different proton numbers, none are isotopes. [1]
Marking note: If a student states "none" with a valid explanation, award full marks. If the question intended two particles to share a proton number, the data in this version does not support that — the answer "none" is correct here.
(d) P has proton number 11 (sodium, Na). It loses 1 electron to form Na⁺. Q has proton number 17 (chlorine, Cl). It gains 1 electron to form Cl⁻. [1]
The compound formed is NaCl (sodium chloride). [1]
The bonding is ionic bonding — electrostatic attraction between oppositely charged ions (Na⁺ and Cl⁻). [1]
Marking note: Award 1 mark for identifying the elements, 1 mark for the correct formula, 1 mark for naming ionic bonding. [3]
17.
(a) Substance X is diamond (or silicon). [1]
Marking note: Diamond is the most common example of a tetrahedral giant covalent structure with very high melting point and no electrical conductivity. Silicon also fits. Accept either.
(b) Diamond has a giant covalent (macromolecular) structure where each carbon atom is covalently bonded to four other carbon atoms in a tetrahedral arrangement. [1]
A large number of strong covalent bonds must be broken to melt diamond, which requires a very large amount of energy. Hence, diamond has a very high melting point. [1]
(c) In diamond, all four valence electrons of each carbon atom are used in covalent bonds. [1]
There are no free or delocalised electrons, and there are no ions. Since there are no charged particles free to move, diamond does not conduct electricity. [1]
18.
(a) Sodium (Na) has electronic configuration 2, 8, 1. It loses 1 electron from its outer shell to form Na⁺ with configuration 2, 8. [1]
Chlorine (Cl) has electronic configuration 2, 8, 7. It gains 1 electron to form Cl⁻ with configuration 2, 8, 8. [1]
The electron transferred from sodium is accepted by chlorine. The resulting Na⁺ and Cl⁻ ions are held together by strong electrostatic forces of attraction (ionic bonding) to form sodium chloride, NaCl. [1]
(b) Sodium chloride has a giant ionic lattice structure. [1]
Strong electrostatic forces of attraction (ionic bonds) exist between the oppositely charged Na⁺ and Cl⁻ ions. A large amount of energy is needed to overcome these strong forces, so NaCl has a high melting point. [1]
(c) Electrolysis of molten sodium chloride to extract sodium metal. / Use in electrolysis. [1]
Marking note: Any valid use that depends on electrical conductivity of molten/dissolved NaCl. Accept "electrolysis" as a general answer.
19.
(a)
Substance A: Simple molecular structure (covalent molecules with weak intermolecular forces) [1]
Substance B: Giant ionic structure (ionic lattice) [1]
Substance C: Giant metallic structure (metallic lattice with delocalised electrons) [1]
(b)
Substance A: Carbon dioxide, CO₂ / Water, H₂O / Methane, CH₄ / Iodine, I₂ [1]
Substance B: Sodium chloride, NaCl / Magnesium oxide, MgO / Calcium fluoride, CaF₂ [1]
Substance C: Copper, Cu / Iron, Fe / Aluminium, Al / Graphite, C [1]
Marking note: Accept any valid example. Graphite is acceptable for C as it is a non-metal with giant covalent structure that conducts electricity.
20.
(a)
Substance D: Simple molecular (covalent) structure — low boiling point, no conductivity in any state. [1]
Substance E: Giant ionic structure — high boiling point, conducts when liquid (ions mobile) but not in solid state. [1]
Substance F: Giant metallic structure — very high boiling point, conducts in both solid and liquid states due to delocalised electrons. [1]
(b) Substance D has a simple molecular structure with weak intermolecular forces (van der Waals forces) between molecules. [1]
Little energy is needed to overcome these weak forces, so D has a low boiling point. [1]
Substance E has a giant ionic structure with strong electrostatic forces between ions. A large amount of energy is needed to overcome these strong ionic bonds, so E has a high boiling point. [1]
Marking note: Must compare the types of forces/structures, not just state the boiling points.
(c) Substance F has a metallic structure. [1]
The metal atoms release their outer shell electrons, which become delocalised and are free to move throughout the structure. These mobile delocalised electrons carry electrical charge, so F conducts electricity in the solid state. [1]
End of Answer Key