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How many pairs of electrons are shared between the two nitrogen atoms in an N₂ molecule?
- a) One pair
- b) Four pairs
- c) Two pairs
- d) Three pairs ✓ (correct answer)
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A substance has a high melting point, does not conduct electricity as a solid, and conducts when molten. Which bonding type best explains these properties?
- a) Simple covalent bonding, with molecules mobile when molten
- b) Metallic bonding, with electrons mobile in the solid
- c) Covalent network bonding, with molecules mobile in the liquid
- d) Ionic bonding, with ions mobile in the molten substance ✓ (correct answer)
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Which set of properties is most consistent with a simple covalent substance?
- a) High melting point; conducts only when dissolved in water
- b) Low melting point; does not conduct electricity as a solid or liquid ✓ (correct answer)
- c) Low melting point; conducts electricity as a solid
- d) High melting point; conducts electricity as a solid and liquid
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Which statement best describes an ionic bond?
- a) A strong electrostatic attraction between oppositely charged ions ✓ (correct answer)
- b) A shared pair of electrons between two nonmetal atoms
- c) An attraction between positive ions and delocalized electrons
- d) A weak attraction between separate molecules
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Magnesium has two outer-shell electrons, and chlorine has seven. Which ions form when magnesium chloride forms?
- a) One Mg²⁻ ion and two Cl⁺ ions
- b) One Mg²⁺ ion and two Cl⁻ ions ✓ (correct answer)
- c) One Mg⁺ ion and one Cl⁻ ion
- d) Two Mg⁺ ions and one Cl²⁻ ion
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Which description correctly shows how sodium chloride forms? Each dot or cross represents an outer-shell electron.
- a) Chlorine transfers one electron to sodium, forming Na⁻ and Cl⁺ ions
- b) Sodium and chlorine share one pair of electrons, forming neutral atoms
- c) Sodium transfers one electron to chlorine, forming Na⁺ and Cl⁻ ions ✓ (correct answer)
- d) Sodium transfers two electrons to chlorine, forming Na²⁺ and Cl²⁻ ions
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An ionic solid does not conduct electricity, but it conducts when molten. Why?
- a) The positive ions become fixed while negative ions move through the liquid
- b) The electrons become shared between molecules when the solid melts
- c) The ions can move through the molten substance and carry charge ✓ (correct answer)
- d) The atoms become neutral and carry charge through the liquid
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Which description of metallic bonding also helps explain why metals can be bent or hammered into shape?
- a) Positive and negative ions form a rigid lattice that breaks when layers shift
- b) Molecules are held together by weak attractions that let them slide apart
- c) Positive ions are surrounded by delocalized electrons, allowing layers of ions to shift ✓ (correct answer)
- d) Atoms share fixed electron pairs, which keep each layer in place
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Which description of the outer electrons in a water molecule is correct?
- a) Each hydrogen shares one pair with the other hydrogen and not with oxygen
- b) Oxygen transfers one electron to each hydrogen, forming three ions
- c) Oxygen shares two pairs with each hydrogen and has no lone pairs
- d) Oxygen shares one pair with each hydrogen and has two lone pairs ✓ (correct answer)
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A simple covalent substance does not conduct electricity. What is the best explanation?
- a) It has no mobile ions or delocalized electrons to carry charge ✓ (correct answer)
- b) Its delocalized electrons are held tightly inside each molecule
- c) Its atoms conduct charge only when they are arranged in layers
- d) Its ions are fixed in a lattice in every physical state