1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Chemistry question on electron affinity

  1. May 26, 2009 #1
    1. The problem statement, all variables and given/known data
    under the same conditions which one of the following atoms will liberate the largest amount of energy when it gains an electron?
    1.Na(g) 2.Ar(g) 3.Li(g) 4.N(g) 5.Mg(g)

    2. Relevant equations

    3. The attempt at a solution
    I was told the answer's N 'cos it's the most electronegative atom out of the choices given but when we consider the electronic configurations of the above atoms Na & Li seems to attain a stable octet by gaining an electron so it would release alot more energy than N which by gaining an electron becomes 2p4 which is far less stable than 2p3.

    so I think its between Li & Na and since Li has a smaller covalent radius it would probably attract the electron more and so release more energy,am I right?
  2. jcsd
  3. May 27, 2009 #2


    User Avatar
    Homework Helper
    Gold Member

    Na, Li, attain stable octets by losing an electron, Mg by losing two.
  4. May 28, 2009 #3
    I'm sorry but I don't get it .
    Alkaline metals like Na and Li usually attain stable octets by losin an electron but, they may also attain stable octets by gaining an electron,no?

    I got down the electron affinity values from http://hyperphysics.phy-astr.gsu.edu/HBASE/chemical/eleaff.html" [Broken]
    but now I'm even more confused,

    The EA values show that EA of Li > Na>N , also that group 2 and 8A elements don't form anions so the answer has to be Li. But,
    what I don't understand is how these values are determined?
    n why does N have an EAof 0 and the other group 5A elements have Electron Affinities which increase downwards ,
    while in other groups, there seems to be a gradual decrease in EA values down their respective groups except, ofcourse, the irregularity seen between O , S in group 5 and F , Cl in group7,also which unsurprisingly I don't understand?
    Last edited by a moderator: May 4, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook