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Homework Help: Choose the element in each of the sets you would expect to have the highest IE2

  1. Jun 14, 2016 #1
    1. The problem statement, all variables and given/known data
    Choose the element in each of the sets you would expect to have the highest IE2.

    a. K
    b. Be
    c. Mg
    d. Ca
    e. Al

    2. Relevant equations
    The correct answer is K

    3. The attempt at a solution
    I do not understand why it is K ...I kind of guessed by using my Ionization Energy diagram that shows the trend on the periodic table as:

    --------> IE increases across a period/row
    IE decreases down a group

    Can someone please explain why K is correct?
  2. jcsd
  3. Jun 14, 2016 #2


    User Avatar

    Staff: Mentor

    What do you know about number of valence electrons in elements? How does it depend on the the element position in the periodic table? Why do the valence electrons are valence electrons?
  4. Jun 14, 2016 #3
    That's a general trend.But there are exceptions. Besides you have to compare IE2.So this can't be used.
    After 1st Ionisation K attains the EC of nearest noble gas i.e. Argon which means it is highly stable.So IE2 of K is highest.
    On the other hand if you see Be,Mg,Ca then the outer shell EC of these elements after 1st ionisation is ns1.So they can easily ionise to gain stability.

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