A Level H1 Chemistry Atomic Structure Bonding Quiz

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A-Level Chemistry H1 Quiz - Atomic Structure Bonding

Name: __________________________
Class: __________________________
Date: __________________________
Score: _______ / 40

Duration: 45 minutes
Total Marks: 40

Instructions:

1. Answer all questions.
2. Write your answers in the spaces provided.
3. The number of marks is given in brackets [ ] at the end of each question or part question.
4. You may use a scientific calculator.
5. A Data Booklet is provided for reference.

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Section A: Atomic Structure and Subatomic Particles

1. Complete the table below to show the composition of the specified particles. [3]

Particle	Protons	Neutrons	Electrons
$^{19}_{9}\text{F}^-$
$^{27}_{13}\text{Al}^{3+}$
$^{14}_{7}\text{N}$

2. Define the term isotope. [2]

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3. Chlorine exists as two stable isotopes, $^{35}\text{Cl}$ and $^{37}\text{Cl}$. The relative atomic mass ($A_r$) of chlorine is 35.5. Calculate the percentage abundance of $^{35}\text{Cl}$ in a sample of chlorine. [2]

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4. The first seven ionisation energies of an element X are shown below.

Ionisation Number	1st	2nd	3rd	4th	5th	6th	7th
Energy / kJ mol$^{-1}$	578	1817	2745	11578	14831	18378	23326

(a) Identify the group in the Periodic Table to which element X belongs. [1]

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(b) Explain your answer to (a) by referring to the data provided. [2]

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Section B: Chemical Bonding and Structure

5. Draw a 'dot-and-cross' diagram to show the bonding in magnesium chloride, $\text{MgCl}_2$. Show outer electrons only. [2]

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6. Aluminium chloride ($\text{AlCl}_3$) can react with ammonia ($\text{NH}_3$) to form an adduct, $\text{Cl}_3\text{AlNH}_3$.

(a) Name the type of bond formed between the aluminium atom and the nitrogen atom in this adduct. [1]

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(b) Explain how this bond is formed, stating clearly which species provides the electrons. [2]

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7. Consider the molecules $\text{BF}_3$ and $\text{NF}_3$.

(a) Draw the shape of the $\text{BF}_3$ molecule and state the bond angle. [2]

Shape:

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Bond Angle: __________________

(b) Draw the shape of the $\text{NF}_3$ molecule and state the bond angle. [2]

Shape:

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Bond Angle: __________________

(c) Explain why the bond angles in $\text{BF}_3$ and $\text{NF}_3$ are different. [2]

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8. Silicon(IV) oxide ($\text{SiO}_2$) and carbon dioxide ($\text{CO}_2$) are both oxides of Group 14 elements. However, $\text{SiO}_2$ is a solid with a very high melting point, whereas $\text{CO}_2$ is a gas at room temperature.

Explain this difference in terms of structure and bonding. [3]

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Section C: Intermolecular Forces and Properties

9. Ethanol ($\text{CH}_3\text{CH}_2\text{OH}$) and dimethyl ether ($\text{CH}_3\text{OCH}_3$) are structural isomers with the same molecular formula, $\text{C}_2\text{H}_6\text{O}$. Ethanol has a boiling point of 78 °C, while dimethyl ether has a boiling point of -24 °C.

Explain why ethanol has a much higher boiling point than dimethyl ether. [3]

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10. Which of the following substances exhibits hydrogen bonding? [1]

A. $\text{CH}_4$ B. $\text{H}_2\text{S}$ C. $\text{HF}$ D. $\text{HCl}$

11. Describe the structure and bonding in solid copper. Explain why copper is a good conductor of electricity. [3]

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12. The table below shows the boiling points of the Group 17 hydrides.

Hydride	Boiling Point / °C
$\text{HF}$	20
$\text{HCl}$	-85
$\text{HBr}$	-67
$\text{HI}$	-35

(a) Explain the trend in boiling points from $\text{HCl}$ to $\text{HI}$. [2]

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(b) Explain why $\text{HF}$ has a significantly higher boiling point than $\text{HCl}$, despite having a lower molecular mass. [2]

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Section D: Application and Analysis

13. The triiodide ion, $\text{I}_3^-$, is formed when iodine reacts with iodide ions. Draw the dot-and-cross diagram for the $\text{I}_3^-$ ion. Show outer electrons only. [2]

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14. Graphite and diamond are both allotropes of carbon.

(a) State one physical property in which graphite and diamond differ. [1]

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(b) Explain this difference in terms of their structure and bonding. [2]

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15. Sodium metal reacts with chlorine gas to form sodium chloride. Describe the changes in the electronic configuration of the sodium and chlorine atoms during this reaction. [2]

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16. Which of the following molecules is non-polar? [1]

A. $\text{H}_2\text{O}$ B. $\text{NH}_3$ C. $\text{CCl}_4$ D. $\text{CHCl}_3$

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

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18. The bond energy of the $\text{N}\equiv\text{N}$ triple bond is very high (945 kJ mol$^{-1}$). Explain why nitrogen gas ($\text{N}_2$) is chemically inert at room temperature. [1]

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19. In the molecule ethene ($\text{C}_2\text{H}_4$), describe the nature of the carbon-carbon double bond in terms of sigma ($\sigma$) and pi ($\pi$) bonds. [2]

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20. A student suggests that because $\text{CO}_2$ contains polar $\text{C=O}$ bonds, the $\text{CO}_2$ molecule must be polar. Is the student correct? Explain your answer. [2]

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A-Level Chemistry H1 Quiz - Atomic Structure Bonding (Answer Key)

1. [3 marks]

• $^{19}_{9}\text{F}^-$: Protons: 9, Neutrons: 10, Electrons: 10 [1]
• $^{27}_{13}\text{Al}^{3+}$: Protons: 13, Neutrons: 14, Electrons: 10 [1]
• $^{14}_{7}\text{N}$: Protons: 7, Neutrons: 7, Electrons: 7 [1]

2. [2 marks] Atoms of the same element [1] with the same number of protons (atomic number) but different numbers of neutrons (mass number/nucleon number). [1]

3. [2 marks] Let $x$ be the abundance of $^{35}\text{Cl}$. Then $(100-x)$ is the abundance of $^{37}\text{Cl}$. $35.5 = \frac{35x + 37(100-x)}{100}$ [1] $3550 = 35x + 3700 - 37x$ $2x = 150$ $x = 75$ Percentage abundance of $^{35}\text{Cl}$ is 75%. [1]

4. (a) Group 13 (or III) [1] (b) There is a large jump in ionisation energy between the 3rd and 4th ionisation energies (from 2745 to 11578 kJ mol$^{-1}$). [1] This indicates that the first 3 electrons are removed from the outer shell, and the 4th electron is removed from an inner shell closer to the nucleus with less shielding. [1]

5. [2 marks]

• Mg ion shown as $[\text{Mg}]^{2+}$ with no outer electrons (or empty shell). [1]
• Two Cl ions shown as $[\text{Cl}]^-$ with 8 outer electrons (crosses/dots clearly distinguished). [1]
• Note: Charges must be correct.

6. (a) Dative covalent bond (or coordinate bond). [1] (b) The nitrogen atom in ammonia has a lone pair of electrons. [1] The aluminium atom in $\text{AlCl}_3$ is electron-deficient (has an empty orbital). The nitrogen atom donates both electrons in the lone pair to form the bond with aluminium. [1]

7. (a) Shape: Trigonal planar. [1] Bond Angle: 120°. [1] (b) Shape: Trigonal pyramidal. [1] Bond Angle: 107° (accept 106°–107.5°). [1] (c) $\text{BF}_3$ has 3 bond pairs and 0 lone pairs on the central atom, so repulsion is equal. [1] $\text{NF}_3$ has 3 bond pairs and 1 lone pair on the central atom. The lone pair-bond pair repulsion is greater than bond pair-bond pair repulsion, compressing the bond angle. [1]

8. [3 marks]

• $\text{SiO}_2$ has a giant molecular (giant covalent) structure with strong covalent bonds throughout the lattice requiring much energy to break. [1]
• $\text{CO}_2$ consists of simple molecular structures. [1]
• The intermolecular forces (van der Waals forces) between $\text{CO}_2$ molecules are weak and require little energy to overcome. [1]

9. [3 marks]

• Ethanol molecules can form hydrogen bonds between the H of the -OH group and the lone pair on the O of another molecule. [1]
• Dimethyl ether molecules cannot form hydrogen bonds with each other (no H attached to O/N/F); they only have permanent dipole-dipole forces and van der Waals forces. [1]
• Hydrogen bonds are stronger than van der Waals/dipole-dipole forces, requiring more energy to overcome. [1]

10. C [1] ($\text{HF}$ has H bonded to highly electronegative F).

11. [3 marks]

• Structure: Giant metallic lattice consisting of $\text{Cu}^{2+}$ (or positive) ions. [1]
• Bonding: Delocalised valence electrons move freely throughout the structure. [1]
• Conductivity: The delocalised electrons are mobile and can carry charge/current when a potential difference is applied. [1]

12. (a) [2 marks]

• The number of electrons increases from $\text{HCl}$ to $\text{HI}$, so the size of the electron cloud increases. [1]
• This leads to stronger van der Waals (London dispersion) forces between molecules, requiring more energy to overcome. [1]

(b) [2 marks]

• $\text{HF}$ molecules form hydrogen bonds due to the high electronegativity of Fluorine and the H-F bond polarity. [1]
• Hydrogen bonds are significantly stronger than the van der Waals forces present in $\text{HCl}$. [1]

13. [2 marks]

• Central I atom bonded to two terminal I atoms. [1]
• Correct display of lone pairs: Central I has 3 lone pairs (or 2 depending on representation of dative nature, but standard A-level often accepts linear with 3 lone pairs on central if treating as resonance/hypervalent, OR 2 lone pairs and dative arrow).
  • Standard Acceptable Answer: Linear shape. Central I has 2 bond pairs and 3 lone pairs. Each terminal I has 1 bond pair and 3 lone pairs. Overall charge -1. [1 for structure/bonds, 1 for lone pairs/charge].
  • Alternative (Dative): One covalent bond, one dative bond from I- to I2.

14. (a) Hardness (Diamond is hard, Graphite is soft/slippery) OR Electrical Conductivity (Graphite conducts, Diamond does not). [1] (b) If Hardness chosen: Diamond has a rigid tetrahedral giant covalent structure with strong covalent bonds in 3D. Graphite has layers held by weak van der Waals forces which can slide. [2] If Conductivity chosen: Graphite has delocalised electrons between layers that can move. Diamond has all electrons fixed in covalent bonds. [2]

15. [2 marks]

• Sodium atom loses one electron from its outer shell to form $\text{Na}^+$ (stable octet). [1]
• Chlorine atom gains one electron into its outer shell to form $\text{Cl}^-$ (stable octet). [1]

16. C [1] ($\text{CCl}_4$ is tetrahedral and symmetrical, so dipoles cancel).

17. [2 marks]

• Ionic compounds consist of a giant lattice of oppositely charged ions. [1]
• There are strong electrostatic forces of attraction between the ions that require a large amount of energy to overcome. [1]

18. [1 mark] The triple bond is very strong and requires a large amount of activation energy to break.

19. [2 marks]

• The double bond consists of one sigma ($\sigma$) bond formed by head-on overlap of orbitals. [1]
• And one pi ($\pi$) bond formed by the sideways overlap of p-orbitals. [1]

20. [2 marks]

• No, the student is incorrect. [1]
• Although the C=O bonds are polar, the $\text{CO}_2$ molecule is linear. The bond dipoles are equal and opposite, so they cancel out, resulting in a non-polar molecule. [1]