chemical bonding

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chemical bonding
2011-11-08 13:45:15

chapter 5
Show Answers:

  1. define compound
    substance that is made up of two or more different elements chemically combined
  2. define chemical bonds
    attractive force that holds atoms together
  3. state the octet rule
    when bonding occurs, atoms tend to reach an electron arrangement with eight electrons in the outermost shell
  4. exceptions to octet rule
    • >transition metals
    • >elements near helium (hydrogen, lithium etc)
  5. define ion
    charged atom or group of atoms
  6. define ionic bond
    force of attraction between oppositely charged ions in a compound
  7. what is crystal lattice
    three-dimensional arrangement of ions
  8. define chemical formula
    way of representing a compound using symbols for the atoms present and numbers to show how many atoms of each element are present
  9. hydroxide ion
  10. nitrate ion
  11. hydrogencarbonate ion
  12. permanganate ion
  13. why do transition metals have variable valency?
    there is such a small energy difference between the 4s and thr 3d subshell
  14. ends in -ide
    compound that just contains two elements
  15. ends in -ate
    contains oxygen as well as the other two elements
  16. why are scandium and zinc not considered transition metals?
    • >scandium can only form Sc3+ ions and zinc can only form Zn2+ions
    • >they only form white compounds
    • >shows little catalytic activity
  17. define transition metals
    forms at least one ion with a partially filled d subshell
  18. when are ionic compounds normally formed?
    when metals react with non-metals
  19. define molecule
    group of atoms joined together
  20. what is a covalent bond
    sharing of a pair of electrons
  21. define valency of an element
    number of atoms of hydrogen or any other monovalent element with which each atom of the element combines
  22. sigma bond
    head on overlapping
  23. pi
    sideways overlap
  24. characteristics of ionic compounds
    • >difficult to cut
    • >usually hard and brittle
    • >contain a network of ions in the crystal
    • >high melting point
    • >high boiling point
    • >usually solid at room temp
    • >conduct electricity when molten or dissolved in water
  25. characteristic of covalent compound
    • >contain individual molecules
    • >usually soft
    • >low melting point
    • >low boiling point
    • >usually liquids, gases or soft solid at r.t
    • >do not conduct electricity
  26. carbonate ion
  27. what does VSEPR stand for?
    valence shell electron pair repulsion theory
  28. what does the VSEPR theory state?
    shape of a molecule depends on the number of pairs of electrons in the valence shell of the central atom
  29. linear
  30. triangular planar
  31. tetrahedron
  32. pyramidal
  33. v-shaped
  34. define electronegativity
    relative attraction that an atom in a molecule has for a shared pair of electrons in a covalent bond
  35. uses of electronegativity values
    • >to predict polarity of covalent bonds
    • >to predict which compounds are ionic and which are covalent
  36. what is a polar molecule
    centre of positive charge and the centre of negative charge coincide
  37. electronegativity difference of more that 1.7
    ionic bonding
  38. electronegativity difference of less than 1.7 or equal to
  39. exceptions to the 1.7 rule
    • >LiH
    • >NaH
    • >KH
    • >CaH2

    they ionic, contain H-
  40. define van der waals forces
    weak attractive forces between molecules resulting from the formation of temporary dipoles
  41. define dipole-dipole forces
    force of attraction between the negative pole of one molecule and the positive pole of another
  42. what does hydrogen bond with
    N, O, F