Chemistry 9: Atom Combining Worksheet

Unit 3: Atom Combining Worksheet

• Worksheet topic: Atom Combining
• Subject: Chemistry 0620
• Grade: 9
• Semester: First Semester 2024/2025
• Exam board/programme: IGCSE
• Teacher: Rasha N. Maraqa

Question 1: Potassium Fluoride Ions

• Question: Which diagram correctly shows the ions in potassium fluoride?
• Options: Four diagrams (A, B, C, and D) are provided and labelled with K+ or K− and F+ or F− with electronic configurations
• Answer: The correct diagram shows potassium ion (K+) and fluoride ion (F−) with their respective electron configurations.

Question 2: Covalent Compound Formula

• Question: What is the formula of the covalent compound formed by atoms X and Y, given their electronic structures?
• Options: Four options (A, B, C, and D) are provided with formulas (XY5, XY3, XY, X3Y)
• Answer: The correct formula is XY.

Question 3: Magnesium Oxide Formula

• Question: What is the formula of the product formed when two atoms of magnesium react with one molecule of oxygen?
• Options: Four options (A, B, C, and D) are provided with formulas (MgO, MgO2, Mg2O, Mg2O2)
• Answer: The correct formula is MgO.

Question 4: Bonding Type

• Question: Identify the type of bonding in compounds X and Y, given their properties.
  • Compound X melts at 801 °C and is a good electrical conductor when dissolved in water.
  • Compound Y boils at 77 °C, is insoluble in water, and is a non-conductor of electricity.
• Options: Four options (A, B, C, and D) are provided with combinations of covalent/ionic bonding for both X and Y.
• Answer: The correct answer is ionic bonding for X and covalent bonding for Y.

Question 5: Methane Diagram

• Question: Which diagram correctly represents the arrangement of outer electrons in a methane molecule?
• Options: Four diagrams (A, B, C, and D) are provided.
• Answer: The correct answer is the matching diagram with a central carbon atom and four outer-shell electrons bonding with four hydrogen atoms.

Question 6: Silicon(IV) Oxide Structure

• Question: Describe the structure of silicon(IV) oxide (SiO2) and list three common properties between silicon(IV) oxide and diamond.
• Answer: Silicon(IV) oxide has a giant/network covalent structure where silicon atoms form strong covalent bonds with four oxygen atoms, creating a continuous, three-dimensional network. Common properties shared with diamond include: -High melting point -Hardness -Insoluble in water

Question 7: Compound Formulae

• Question: Deduce the formulae for chromium(III) sulfate and barium hydroxide using provided ions.
• Answer: Cr2(SO4)3 and Ba(OH)2

Question 8: Third Period Elements

• Question: Explain why Na, Mg, and Al are good conductors of electricity, identify the diatomic molecule, and explain why silicon has the highest melting point in the third period.
• Answer: These elements have delocalized electrons, which can move freely. The element that exists as a diatomic molecule of the type X2 is chlorine (Cl2). Silicon's very high melting point is contributed to its giant covalent structure.

Question 9: Lithium Bromide Electrolysis

• Question: Explain the motion of ions in solid lithium bromide, and define the term 'ionic bond' and 'ionic lattice.
• Answer: The ions in solid lithium bromide do not move, they are fixed in the solid. An ionic bond is the electrostatic attraction between oppositely charged ions. An 'ionic lattice' is a regular arrangement of positive and negative ions.

Question 10: Substances Properties

• Question: Match substances (A-E) with their descriptions (covalent/ionic solid, etc.), based on the table of their melting/boiling points and conductivity properties.

Question 11: Calcium Nitride Diagram

• Question: Draw a diagram of calcium nitride (Ca3N2), showing the charges on the ions and the arrangement of electrons.

Question 12: Graphite Lubrication

• Question: Explain why graphite can be used as a lubricant.
• Answer: Graphite contains delocalized electrons that move freely throughout the structure. The weak forces of attraction between the layers allow the layers to move over each other easily.

Question 13: Shared Electrons

• Question: Identify compounds where electrons are shared between atoms.
• Answer: Methane (CH4), lead bromide (PbBr2), and sodium chloride (NaCl).

Question 14: Drill Tip Materials

• Question: Identify correct statements about materials used for drill tips and lubricants.
• Answer: Diamond is hard and does not conduct electricity, making it suitable for drill tips. Graphite is soft and conducts electricity, making it a suitable lubricant.

Question 15: Carbon Containing Substances

• Question: Classify the substances (A to F) containing carbon based on their structures.

Question 16: Magnesium Chloride Ions

• Question: Draw diagrams to show the electronic structures of magnesium and chloride ions in magnesium chloride (MgCl2), indicating the charges.

Question 17: Ethyne Dot-and-Cross Diagram

• Question: Draw a dot-and-cross diagram for ethyne (H−C≡C−H), displaying outer shell electrons.

Question 18: Hydrogen Sulfide Dot-and-Cross Diagram

• Question: Draw a dot-and-cross diagram for hydrogen sulfide (H2S), showing outer shell electrons.

Question 19: Hydrogen Sulfide Boiling Point

• Question: Describe why hydrogen sulfide has a low boiling point.
• Answer: The weak intermolecular forces between simple molecules result in a low boiling point.

Question 20: Chlorine Molecule Dot-and-Cross Diagram

• Question: Draw a dot-and-cross diagram for a chlorine molecule (Cl2).

Question 21: Substance Properties (R, S, T, U)

• Question: Identify and classify four compounds, R, S, T, and U (based on diagrams) by identifying their properties (e.g., ionic structure, electrical conductivity when solid).

Question 22: Covalent Bonding (R, S, T, U)

• Question: Identify two covalent bonded substances among R, S, T, or U.

Question 23: Potassium Iodide Properties

• Question: Describe the electron transfer between potassium and iodine atoms to form potassium iodide (KI). Explain the structure of potassium iodide and the reason for its high melting point.

Question 24: Carbon Dioxide Conductivity

• Question: Explain why carbon dioxide is a non-conductor of electricity in terms of particles

Question 25: Silicon(IV) Oxide Properties

• Question: Describe the structure of silicon (IV) oxide (SiO2) as a macromolecule. Also list three common properties shared by silicon (IV) oxide and diamond.

Question 26: Ion Formulae

• Question: Deduce the formulas for selenide and gallium ions.

Question 27: Lithium Bromide Electrolysis

• Question: Explain why solid lithium bromide is a poor conductor of electricity. Define ionic bonding and ionic lattice.

Question 28: Graphite and Diamond Structures

• Question: Describe the structures of graphite and diamond

Question 29: Strontium Oxide Diagram

• Question: Draw a diagram of strontium oxide (SrO) showing the charges on the ions and the arrangement of valence electrons.

Question 30: Graphite Properties (Structure Explanation)

• Question: (a) Explain graphite's softness and electrical conductivity using its structure. (b) Explain diamond's hardness using its structure. (c) Compare graphite and diamond's electrical conductivity based on structure. (d) Provide two uses of graphite based on its properties.