O Level Chemistry Atomic Structure Bonding Quiz

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O-Level Chemistry Quiz - Atomic Structure Bonding

Name: ____________________
Class: ____________________
Date: ____________________
Score: ________ / 45

Duration: 60 Minutes
Total Marks: 45

Instructions:

• Answer all questions in the spaces provided.
• Use a pencil for diagrams and a pen for written responses.
• Show all working for calculations.

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Section A: Atomic Structure (Questions 1–7)

1. Define the term isotope. [1]
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2. An atom of element X has 13 protons and 14 neutrons. (a) State the nucleon number of element X. [1] \

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   (b) Write the nuclide notation for this atom. [1] \

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3. Explain why atoms are electrically neutral. [1]
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4. Element Y is in Group 17 of the Periodic Table. (a) State the electronic configuration of the most stable ion of element Y. [1] \

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   (b) Explain how element Y achieves this stable electronic configuration. [1]
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5. Compare the properties of an atom and an ion of the same element. State one similarity and one difference. [2]
   Similarity: ________________________________________________________________ Difference: _______________________________________________________________

6. An ion of element Z has the formula $Z^{2+}$. It has 10 electrons. Determine the proton number of element Z. [1]
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7. Explain, with reference to electronic structure, why Argon is chemically inert. [2]
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Section B: Ionic and Covalent Bonding (Questions 8–14)

8. Describe the process of ion formation when a metal reacts with a non-metal. [2]
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9. Draw a dot-and-cross diagram to show the bonding in a molecule of water ($\text{H}_2\text{O}$). Show only the valence electrons. [2]
   
   
   
   
   
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10. Draw a dot-and-cross diagram for the compound formed between Magnesium (Mg) and Chlorine (Cl). Show only the valence electrons. [2]
    
    
    
    
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11. Explain why ionic compounds have high melting points. [2]
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12. Define a covalent bond. [1]
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13. Draw a dot-and-cross diagram for the hypochlorite ion ($\text{ClO}^-$). Show only outer electrons. [2]
    
    
    
    
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14. Explain why methane ($\text{CH}_4$) has a much lower boiling point than sodium chloride ($\text{NaCl}$). [3]
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Section C: Metallic Bonding and Giant Structures (Questions 15–20)

15. Describe the structure of a metal in terms of cations and electrons. [2]
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16. Explain why metals are malleable, whereas giant covalent structures like diamond are brittle. [3]
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17. Draw a labelled diagram to show the structure of copper metal. [2]
    
    
    
    
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18. Compare the electrical conductivity of diamond and graphite. Explain the difference in terms of their bonding. [3]
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19. Silicon(IV) oxide ($\text{SiO}_2$) has a very high melting point. Explain this observation. [2]
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20. An alloy is a mixture of a metal with another element. Explain why alloys are generally harder than pure metals. [3]
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Answer Key - Atomic Structure Bonding Quiz

1. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. (1)

2. (a) $13 + 14 = 27$ (1) (b) $^{27}_{13}\text{X}$ (1)

3. Because the number of positively charged protons in the nucleus is equal to the number of negatively charged electrons orbiting the nucleus. (1)

4. (a) 2, 8, 7 (or 2, 8, 18, 7 etc. depending on period) $\rightarrow$ Ion: 2, 8, 8 (1) (b) Element Y gains one electron to achieve a full outer shell of electrons (stable octet). (1)

5. Similarity: Same number of protons / Same chemical properties. (1) Difference: Different number of electrons / Different charge. (1)

6. Electrons in $Z^{2+} = 10$. Therefore, neutral atom has 12 electrons. Proton number = 12. (1)

7. Argon has a full valence shell (octet). (1) Therefore, it is stable and does not need to gain, lose, or share electrons to react. (1)

8. The metal atom loses valence electrons to form a positive ion. (1) The non-metal atom gains these electrons to form a negative ion. (1)

9. Diagram: Oxygen center with 2 shared pairs (one with each H) and 2 lone pairs. H atoms each with 1 shared electron. (2)

10. Diagram: $[\text{Mg}]^{2+}$ and two $[\text{Cl}]^-$ ions. Mg should have no valence electrons shown; Cl should have 8 electrons (7 cross, 1 dot). (2)

11. Ionic compounds consist of a giant ionic lattice. (1) Strong electrostatic forces of attraction exist between oppositely charged ions, which require significant energy to overcome. (1)

12. A covalent bond is a strong electrostatic attraction between a shared pair of electrons and the nuclei of the two bonded atoms. (1)

13. Diagram: $\text{Cl}$ and $\text{O}$ sharing one pair. Total electrons must account for the $-1$ charge. Brackets around the whole ion with a minus sign. (2)

14. Methane is a simple molecular structure with weak intermolecular forces of attraction. (1) Sodium chloride is a giant ionic lattice with strong electrostatic forces of attraction. (1) Much more energy is required to break the ionic bonds than the intermolecular forces. (1)

15. A regular lattice of positive metal cations (1) surrounded by a "sea" of delocalized electrons. (1)

16. In metals, layers of cations can slide over each other without breaking the metallic bond because delocalized electrons maintain the attraction. (1) In diamond, each carbon is bonded to four others in a rigid tetrahedral structure. (1) Any shift in the lattice breaks the strong covalent bonds, causing the crystal to shatter. (1)

17. Diagram: Regular arrangement of $\text{Cu}^{2+}$ ions with electrons ($\text{e}^-$) scattered throughout. Labels: "Metal cations" and "Delocalized electrons". (2)

18. Graphite conducts electricity; diamond does not. (1) In graphite, each carbon is bonded to three others, leaving one delocalized electron per carbon atom free to move. (1) In diamond, all valence electrons are used in covalent bonding; there are no free electrons to carry charge. (1)

19. $\text{SiO}_2$ has a giant covalent structure. (1) A large number of strong covalent bonds must be broken to melt the substance, requiring high energy. (1)

20. Pure metals have layers of identical atoms that slide easily. (1) In alloys, atoms of different sizes disrupt the regular arrangement of the lattice. (1) This makes it harder for layers to slide over each other. (1)