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What is Eθ?

  1. Jun 29, 2007 #1
    Nowhere in my notes does it say what Eθ is and i cant find a definition of it on the internet :confused:

    I'll give you the context:

    For group 2 of the periodic table, state and explain the trends in the following for their elements:

    (i) redox property, related to Eθ value
     
  2. jcsd
  3. Jun 29, 2007 #2
    I believe that symbol refers to the standard electrode potential. Think of it as the direction of the voltage for an electric current set up using chemical cells to generate the electricity. You can predict some properties and general periodic trends from interpreting it.

    For example, compare Lithium and Bromine:

    Li+ + e- -----> Li Electrode Potential: -3.04 V

    Br2 + 2e- -----> 2Br- Electrode Potential: +1.07

    The relatively large negative electrical potential for lithium can be interpreted to mean that generally an electric current in a chemical cell will favor the left side of the equation which has Lithium giving up electrons to form a cation as opposed to staying as Lithium metal on the right side of the equation (the larger the number, the greater the tendency towards one direction or the other).

    On the other hand, the sign of the electrode potential for Bromine gas is positive which means the right side of that chemical equation is favored over the left (Bromine would tend to accept electrons and form a negative ion as opposed to staying bromine liquid).

    This should match your expectation from early chemistry that Lithium will tend to lose 1 electron in chemical reactions and become positively charged while bromine will gain an electron to become negatively charged (only now with standard electrode potentials you can measure and verify this tendency). That's not all you can get from these values...when you compare the electrode potetials down a column in a periodic table or across rows do you notice any trends showing up?
     
  4. Jun 30, 2007 #3
    yea, i see they decrease down the group.

    this is what i put as an answer to that question:

    The elements in group 2 are all strong reducing agents. The larger the atoms, the easier it is to lose electrons and therefore the reducing power increases down group 2. The standard electrode potential is the value of an elements ability to be reduced. The greater this value, the easier they are to be reduced. Since the group 2 elements undergo oxidation (making them reducing agents), they have very low Eθ values which degrease down group 2.

    does that sound about right?

    thanks for the reply
     
  5. Jun 30, 2007 #4
    It's not a theta, it's a zero with a line thru it. It denotes the electrode potential of something at standard conditions. (pressure, temperature etc.)
     
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