Chapter 4: Structure of Molecules

Chapter 4: Structure of Molecules focuses on how atoms combine to form molecules, the types of chemical bonds, molecular formulas, and the concept of valency. Students will also learn about ionic and covalent bonding, structural formulas, and how these bonds affect the properties of compounds. This chapter helps in understanding the molecular composition of matter and the forces that hold it together.

1. What is the smallest particle of a compound that retains its chemical properties?

  • A. Atom
  • B. Molecule ✅
  • C. Ion
  • D. Proton
Explanation: A molecule is the smallest particle of a compound that retains all of its chemical properties.

2. What type of bond is formed when electrons are transferred from one atom to another?

  • A. Covalent bond
  • B. Ionic bond ✅
  • C. Metallic bond
  • D. Hydrogen bond
Explanation: In ionic bonding, electrons are transferred, creating positively and negatively charged ions.

3. Which of the following represents a covalent compound?

  • A. NaCl
  • B. KBr
  • C. H2O ✅
  • D. CaCl2
Explanation: H2O has covalent bonds where atoms share electrons.

4. What does a structural formula show?

  • A. Mass of each atom
  • B. State of the substance
  • C. Arrangement of atoms and bonds ✅
  • D. Total energy
Explanation: A structural formula depicts how atoms are bonded in a molecule.

5. What is the valency of oxygen in water?

  • A. 1
  • B. 2 ✅
  • C. 3
  • D. 4
Explanation: Oxygen has a valency of 2, allowing it to form two covalent bonds in H2O.

6. Which of the following has a double covalent bond?

  • A. H2
  • B. O2
  • C. CO2
  • D. CH4
Explanation: In CO2, each oxygen forms a double bond with carbon.

7. What term describes molecules with the same molecular formula but different arrangements of atoms?

  • A. Isotopes
  • B. Isomers ✅
  • C. Isobars
  • D. Allotropes
Explanation: Isomers have the same molecular formula but different structures.

8. Which property is typical of ionic compounds?

  • A. Low melting point
  • B. High melting point ✅
  • C. Poor conductor when molten
  • D. Soft and flexible
Explanation: Ionic compounds have strong electrostatic forces, resulting in high melting points.

9. Which of the following bonds is the weakest?

  • A. Ionic bond
  • B. Covalent bond
  • C. Hydrogen bond ✅
  • D. Metallic bond
Explanation: Hydrogen bonds are weaker than ionic or covalent bonds but are important in biological systems.

10. Which formula shows the actual number of atoms of each element in a molecule?

  • A. Empirical formula
  • B. Molecular formula ✅
  • C. Structural formula
  • D. Condensed formula
Explanation: A molecular formula indicates the exact number of each type of atom in a molecule.

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