bonding

• What do metal atoms do to form positive ions?

  Metal atoms lose electrons to form +ve ions.
• What do non-metal atoms do to form negative ions?

  Non-metal atoms gain electrons to form -ve ions.
• How does magnesium change when it forms a Mg2+ ion?


  Mg goes from 1s$^2$ 2s$^2$ 2p$^6$ 3s$^2$ to Mg2+ 1s$^2$ 2s$^2$ 2p$^6$.
• How does oxygen change when it forms an O2- ion?

  O goes from 1s$^2$ 2s$^2$ 2p$^4$ to O2- 1s$^2$ 2s$^2$ 2p$^6$.
• What factors affect the strength of ionic bonding?

  Ionic bonding is stronger and the melting points higher when the ions are smaller and/or have higher charges.
• Why does MgO have a higher melting point than NaCl?

  MgO has smaller ions and higher charges (Mg2+ & O2-) compared to NaCl (Na+ & Cl-).
• What is the structure of ionic crystals?

  Ionic crystals have the structure of giant lattices of ions.
• What is the trend in ionic radii across a period and down a group?

  • Across a period: Ionic radii decrease due to increasing nuclear charge.
  • Down a group: Ionic radii increase due to additional electron shells.

  
• Why are positive ions smaller than their corresponding atoms?

  Positive ions are smaller because they have one less shell of electrons and a higher ratio of protons to electrons.
• Why are negative ions larger than their corresponding atoms?

  Negative ions are larger because they have more electrons than the corresponding atom but the same number of protons.
• What is the definition of ionic bonding?

  Ionic bonding is the electrostatic force of attraction between oppositely charged ions formed by electron transfer.
• What do metal atoms do to form positive ions?

  Metal atoms lose electrons to form +ve ions.
• What is a covalent bond?

  A covalent bond is a shared pair of electrons.
• What do non-metal atoms do to form negative ions?

  Non-metal atoms gain electrons to form -ve ions.
• What is a dative covalent bond?

  A dative covalent bond forms when the shared pair of electrons in the covalent bond come from only one of the bonding atoms.
• What are common examples of molecules that contain dative covalent bonds?

  • NH4⁺
  • H3O⁺
  • NH3BF3
• How does magnesium change when it forms a Mg2+ ion?


  Mg goes from 1s$^2$ 2s$^2$ 2p$^6$ 3s$^2$ to Mg2+ 1s$^2$ 2s$^2$ 2p$^6$.
• What is metallic bonding?


  Metallic bonding is the electrostatic force of attraction between the positive metal ions and the delocalised electrons.
• What are the three main factors that affect the strength of metallic bonding?

  1. Number of protons/Strength of nuclear attraction.
  2. Number of delocalised electrons per atom.
  3. Size of ion.
• How does oxygen change when it forms an O2- ion?

  O goes from 1s$^2$ 2s$^2$ 2p$^4$ to O2- 1s$^2$ 2s$^2$ 2p$^6$.
• How does the metallic bonding in Mg compare to that in Na?

  Mg has stronger metallic bonding than Na due to more outer shell electrons and a smaller ion size.
• What are the properties of ionic bonding?

  • High melting and boiling points due to strong electrostatic forces.
  • Generally good solubility in water.
  • Poor conductivity when solid.
  • Good conductivity when molten.

  
• What factors affect the strength of ionic bonding?

  Ionic bonding is stronger and the melting points higher when the ions are smaller and/or have higher charges.
• What are the properties of molecular (simple) substances?

  • Low melting and boiling points due to weak intermolecular forces.
  • Generally poor solubility in water.
  • Poor conductivity when solid and molten.

  
• What are the properties of macromolecular substances?

  • High melting and boiling points due to strong covalent bonds.
  • Insoluble in water.
  • Poor conductivity when solid.
• Why does MgO have a higher melting point than NaCl?

  MgO has smaller ions and higher charges (Mg2+ & O2-) compared to NaCl (Na+ & Cl-).
• What are the properties of metallic substances?

  • High melting and boiling points due to strong metallic bonding.
  • Good conductivity when solid and molten.
  • Malleable due to identical positive ions in the lattice.

  
• What are the shapes of molecules based on bonding and lone pairs?

  • Linear: 2 bonding pairs, 0 lone pairs (180°)
  • Trigonal planar: 3 bonding pairs, 0 lone pairs (120°)
  • Tetrahedral: 4 bonding pairs, 0 lone pairs (109.5°)
  • Trigonal pyramidal: 3 bonding pairs, 1 lone pair (107°)
  • Bent: 2 bonding pairs, 2 lone pairs (104.5°)
  • Trigonal bipyramidal: 5 bonding pairs, 0 lone pairs (120° and 90°)
  • Octahedral: 6 bonding pairs, 0 lone pairs (90°)
• How do lone pairs affect bond angles?

  Lone pairs repel more than bonding pairs, reducing bond angles by about 2.5° per lone pair.
• What is electronegativity?


  • Electronegativity is the relative tendency of an atom in a covalent bond to attract electrons to itself.
  • F, O, N, and Cl are the most electronegative atoms.
• What factors affect electronegativity?

  • Increases across a period due to more protons and smaller atomic radius.
  • Decreases down a group due to increased distance and shielding of outer electrons.

  
• How many electrons are in the molecule described?

  10 electrons
• What type of molecular shape is formed with 4 bond pairs and 1 lone pair?

  It is a variation of the trigonal bipyramidal shape.
• What is the bond angle in a square planar molecular shape?

  90°
• How does the presence of a lone pair affect bond angles?

  It reduces the bond angle from the ideal value.
• What is the bond angle in a linear molecular shape?

  180°
• What is the definition of electronegativity?

  Electronegativity is the tendency of an atom in a covalent bond to attract electrons to itself.
• Which atoms are the most electronegative?

  F, O, N, and Cl
• How does electronegativity change across a period?

  Electronegativity increases across a period.
• What happens to electronegativity as you move down a group?

  Electronegativity decreases down a group.