Structure 2.3—The metallic model：練習問題

• a.

  Sodium chloride

• b.

  Sulfur

• c.

  Graphite

• d.

  Magnesium

• a.

  The number of valence electrons increases down the group, weakening the lattice.

• b.

  The ionization energy increases down the group, making it harder to maintain the electron sea.

• c.

  The ionic radius increases, which decreases the electrostatic attraction between the nucleus and the delocalized electrons.

• d.

  The density decreases down the group, leading to weaker metallic bonds.

• a.

  Conductivity decreases from \(Na\) to \(Al\) because the ions become larger and impede electron flow.

• b.

  Conductivity remains constant because all three elements utilize a "sea of electrons" model.

• c.

  Conductivity increases because the melting point increases, allowing for higher energy electron transport.

• d.

  Conductivity generally increases from \(Na\) to \(Al\) because the density of delocalized charge carriers per unit volume increases.

• a.

  Localized electrons held tightly by positive ions.

• b.

  Strong directional covalent bonds.

• c.

  Weak intermolecular forces between atoms.

• d.

  A lattice of positive ions surrounded by a sea of delocalized electrons.

• a.

  Increased atomic radius which allows for more overlap of electron shells.

• b.

  Increased shielding of the nucleus by inner-shell electrons.

• c.

  Increased charge on the metal ion and a higher number of delocalized electrons.

• d.

  Decreased electronegativity which makes the valence electrons more stable.

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