Common Senses About Elements

• assign oxidation numbers to H, N, and O in compounds
• understand formation of compounds from s and p block elements
• understand electron configurations of atoms and ions
• understand sizes of positive and negative ions
• know trends of physical properties in periods and groups

Alkali and Alkaline Earth Metals

• know industrial usage of some elements
• know production of Na, K, and Ca in industry
• know flame color of Na, and K
• know formation of alkali metal nitride
• know compounds known as gypsum, Epsom salts, soda ash, baking soda lime, slaked lime, milk of magnesia, caustic soda, etc.
• know ions present in hard water and the "water-softening" process

Chemical Bonding

• understand lattice energy
• know Lewis symbols for elements, ions, and simple molecules
• know octet rules

There are some practice questions in the dialogue. For the DOS version, you have to press the key to write the quiz.

Confidence Building Questions

• In atomic or mole percent, what is the most abundant element in a human body? Enter the symbol for the element.

  If your answer is...I'm lost!
  Consider...
  Water is most abundant chemical in a human body.
  

  If your answer is...H
  Excellent...
  Hydrogen is also the most abundant element in the sun and in the universe.
  

• What is the oxidation number for N in Li₃N? Enter a signed number.

  If your answer is...I'm lost!
  Consider...
  The oxidation numbers for N in Li₃N and NH₃ are the same, -3.
  

  If your answer is...1, +1, -1 or -2
  Consider...
  Li usually has charge +1, and Li₃N is neutral.
  

  If your answer is...-3
  Excellent...
  Li is the only alkali metal that reacts with N₂.
  

• Which of the following ions is the largest?
  Na⁺, K⁺, F^-, Cl^-

  If your answer is...I'm lost!
  Consider...
  All negative ions are larger than positive ions of the same element.
  

  If your answer is...Cl^-
  Excellent...
  You have achieved some understanding of the variation of size over the
  periodic table.
  

• The Haber process is used for the synthesis of what? Give the formula of the compound.

  If your answer is...I'm lost!
  Consider...
  The Haber process uses much H₂ and N₂.
  

  If your answer is...NH₃ or ammonia
  Excellent...
  The reaction is 3 H₂ + N₂ = 2 NH₃
  

• What process will be useful for the production of potassium metal?
  a. reduction by hydrogen
  b. oxidation by fluorine
  c. electrolysis
  d. pyrolysis (decomposition by heating)

  If your answer is...I'm lost!
  Consider...
  The alkali metals can be obtained by electrolysis of their molten salts.
  

  If your answer is...c
  Excellent...
  The electrolysis process forces an oxidation and a reduction.
  

• Which of the following will give a red flame test?
  LiCl, NaOH, KCl, RbI, HBr.

  If your answer is...I'm lost!
  Consider...
  Li-red, Na-yellow, K-violet, Copper halides-green,
  copper compounds other than halides-emerald.
  

  If your answer is...Li
  Consider...
  Na is the key element, but the above lists NaOH
  

  If your answer is...LiCl
  Excellent...
  Na⁺ gives a yellow flame test.
  

• Which of the following group 2 elements has the lowest density?
  Be, Mg, Ca, Sr, Ba.

  If your answer is...I'm lost!
  Consider...
  

  Be,   Mg,   Ca,   Sr,   Ba  (density)
  1.85, 1.74, 1.55, 2.54, 3.5 g/cc
  

  If your answer is...Ca
  Excellent...
  The density of elements in a group usually increases as Z increases.
  

• Which of the following lists gives ions or atoms with the same
  electronic configuration?
  a. H⁺, Li⁺, Na⁺
  b. F^-, Cl^-, Br^-
  c. Cl, Ar⁺, K²⁺
  d. Cl⁺, Ar, Ca²⁺.
  
  Hint . . . c.

  Discussion - Consider the following fact to help you solve the above problem. The three ions H^-, He, Li⁺ all have the electronic of He, or the [He] core. Furthermore, H, He⁺, and Li²⁺ are hydrogen-like atoms.

• Choose the compound for which the lattice energy is the largest.
  MgF₂, MgCl₂, MgBr₂, MgI₂.

  If your answer is...I'm lost!
  Consider...
  

  MgF2,  MgCl2,  MgBr2,  MgI2  lattice energy
  2957,  2526,   2440,   2327  kJ/mol
  

  If your answer is...MgF₂
  Excellent...
  The lattice energy of a compound increases with decreasing ionic radii.
  

• How many coulombs (C) of charge are required to reduce 1 mole
  of K⁺ ion to metal. (electron charge, 1.6022e-19 C,
  Avogadro's number: N = 6.0221e23.)

  If your answer is...I'm lost!
  Consider...
  6.022e23 * 1.6022e-19 C = 96486 C
  

  If your answer is...96486
  Excellent...
  96486 C is known as a Faraday. This question shows you the relationship
  between charge on an electron, Avogadro's number, and Faraday constant.
  

• Electronic assignments in molecules do not always follow the octet rule. Which one of the following molecules does not obey the octet rule?
  HCl, H₂SO₄, SF₆, I₂.

  If your answer is...I'm lost!
  Consider...
  There are six S-F bonds around the S atom.
  

  If your answer is...SF₆
  Excellent...
  There are too many electrons (12) around S in SF₆, 2 for each S-F bond.
  

  ) CChieh@UWaterloo.ca