Secondary 4 Pure Chemistry Atomic Structure Bonding Quiz

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Secondary 4 Pure Chemistry Quiz - Atomic Structure Bonding

Name: ________________________
Class: ________________________
Date: ________________________
Score: ________ / 40

Duration: 60 Minutes
Total Marks: 40
Instructions: Answer all questions. Use a pen. For diagrams, use a pencil. Show all working for calculations.

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Section A: Atomic Structure and Ion Formation

(Questions 1–7)

1. An element $X$ forms an ion of type $X^{2+}$ which has only two completely filled shells of electrons. Identify element $X$. [1]

   Answer: ________________________

2. Define the term isotopes. [1]

   Answer: ___________________________________________________________________________

3. An atom of element $Y$ has 13 protons and 14 neutrons. (a) State the nucleon number of element $Y$. [1]

   Answer: ________________________ (b) Write the nuclide notation for this atom. [1]

   Answer: ________________________

4. Element $Z$ is in Group 17 of the Periodic Table. Describe how element $Z$ achieves a stable electronic arrangement. [2]

   Answer: ___________________________________________________________________________

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5. Explain why the relative atomic mass of Chlorine is 35.5, rather than a whole number. [2]

   Answer: ___________________________________________________________________________

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6. An ion $M^+$ has the electronic configuration 2, 8, 8. (a) Identify the element $M$. [1]

   Answer: ________________________ (b) State the number of electrons in the original atom $M$. [1]

   Answer: ________________________

7. Compare the relative masses and charges of a proton and an electron. [2]

   Answer: ___________________________________________________________________________

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Section B: Chemical Bonding and Diagrams

(Questions 8–14)

8. Draw a "dot and cross" diagram of the electronic structure of magnesium oxide ($\text{MgO}$). Show only the valence shells. [2]

   $\text{Space for diagram:}$ <br><br><br><br>

9. Describe the formation of a covalent bond in terms of electron sharing. [2]

   Answer: ___________________________________________________________________________

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10. Carbon tends to form covalent compounds. Draw the dot-and-cross diagram for methane ($\text{CH}_4$). Show only valence electrons. [3]

    $\text{Space for diagram:}$ <br><br><br><br>

11. Describe the bonding in a metallic lattice. [2]

    Answer: ___________________________________________________________________________

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12. Draw a "dot and cross" diagram of the electronic structure of potassium chloride ($\text{KCl}$). Show only the valence shells. [2]

    $\text{Space for diagram:}$ <br><br><br><br>

13. Explain why ionic compounds generally have high melting points. [2]

    Answer: ___________________________________________________________________________

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14. A compound consists of two elements: one from Group 2 and one from Group 16. (a) State the type of bonding present in this compound. [1]

    Answer: ________________________ (b) Write the general formula for this compound. [1]

    Answer: ________________________

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Section C: Structure and Properties of Materials

(Questions 15–20)

15. Explain, in terms of structure and bonding, why graphite is able to conduct electricity. [3]

    Answer: ___________________________________________________________________________

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16. Diamond is an extremely hard substance. Explain this property with reference to its structure. [3]

    Answer: ___________________________________________________________________________

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17. Compare the electrical conductivity of copper and diamond. Explain your answer. [3]

    Answer: ___________________________________________________________________________

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18. Silicon carbide ($\text{SiC}$) has a structure similar to diamond. State whether $\text{SiC}$ is likely to be: (a) Hard or Soft? [1]

    Answer: ________________________ (b) An electrical conductor or insulator? [1]

    Answer: ________________________

19. Explain why graphite is used as a lubricant in machinery. [3]

    Answer: ___________________________________________________________________________

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20. A substance is found to have a low boiling point and does not conduct electricity in any state. Deduce the type of structure this substance possesses. [2]

    Answer: ___________________________________________________________________________

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Answer Key - Secondary 4 Pure Chemistry Quiz (Atomic Structure Bonding)

1. Beryllium (Be). (Ion $\text{Be}^{2+}$ has configuration 2). [1]
2. Atoms of the same element with the same proton number but different nucleon numbers. [1]
3. (a) 27 [1] (b) $^{27}_{13}\text{Y}$ (or similar nuclide notation) [1]
4. Element $Z$ gains one electron to achieve a stable octet/full outer shell of electrons. [2]
5. Chlorine exists as a mixture of isotopes (mainly $\text{Cl}-35$ and $\text{Cl}-37$). The relative atomic mass is the weighted average of these isotopes. [2]
6. (a) Potassium (K) [1] (b) 19 [1]
7. Mass: Proton is significantly heavier than electron (approx 1836 times). Charge: Proton is positive (+1), electron is negative (-1). [2]
8. Diagram: $\text{Mg}$ ion $[\text{Mg}]^{2+}$ with empty valence shell (or 2,8) and $\text{O}$ ion $[\text{O}]^{2-}$ with 8 electrons in valence shell. Square brackets and charges must be present. [2]
9. A covalent bond is formed when two non-metal atoms share a pair of valence electrons to achieve a stable electronic configuration. [2]
10. Diagram: Carbon in center with 4 bonds to Hydrogen. Each bond shown as a pair of electrons (one dot, one cross). Only valence electrons shown. [3]
11. A lattice of positive metal ions surrounded by a "sea" of delocalized electrons. [2]
12. Diagram: $\text{K}$ ion $[\text{K}]^{+}$ (valence shell empty/2,8,8) and $\text{Cl}$ ion $[\text{Cl}]^{-}$ (valence shell full 2,8,8). Square brackets and charges present. [2]
13. Strong electrostatic forces of attraction between oppositely charged ions exist throughout the giant ionic lattice, requiring significant energy to break. [2]
14. (a) Ionic [1] (b) $\text{MX}$ (where $\text{M}$ is Group 2 and $\text{X}$ is Group 16) [1]
15. Each carbon atom is bonded to three others, leaving one delocalized electron per carbon atom. These electrons are free to move through the layers of the structure, allowing the conduction of electricity. [3]
16. Each carbon atom is covalently bonded to four other carbon atoms in a rigid 3D tetrahedral network. These strong covalent bonds throughout the structure make it extremely hard. [3]
17. Copper conducts electricity; diamond does not. Copper has delocalized electrons in its metallic bonding that can move freely. Diamond has all valence electrons fixed in covalent bonds, so there are no mobile charge carriers. [3]
18. (a) Hard [1] (b) Insulator [1]
19. Graphite consists of layers of carbon atoms. There are weak forces of attraction between the layers, allowing them to slide over each other easily. [3]
20. Simple molecular structure. Low boiling point indicates weak intermolecular forces; lack of conductivity indicates no free ions or delocalized electrons. [2]