Which has the greater affinity for an electron, Si or C and why? When thinking about the exception with F and Cl I would expect Si to have a greater electron affinity than C, but when I look at electron affinity values online I get mixed results. Some charts put C at -122kJ/mol and Si at -134kJ/mol which confirms my assumptions (https://images.app.goo.gl/6dpbc44DjnStpaLk9), but others place C at 153.9 and Si at 133.6 (https://college.cengage.com/chemistry/intro/zumdahl/intro_chemistry/5e/students/protected/periodictables/pt/pt/pt_ea2.html) (also not sure about the units for this chart, I would assume kJ/mol but it doesn't say). Which is correct and why?

  • 2
    $\begingroup$ 153.9 and 133.6 could be the ionization energies of C and Si. $\endgroup$
    – Volpina
    Mar 8 at 20:34
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    $\begingroup$ en.wikipedia.org/wiki/Electron_affinity_(data_page) is quite clear about that. $\endgroup$
    – Mithoron
    Mar 8 at 21:21
  • $\begingroup$ @Volpina thank you for explaining that to me! My professor actually teaches electron affinity as EA= -(ΔH), so I'm used to seeing the positive values and associating it with energy released. I was actually quite confused when I first looked up electron affinity values and saw the negative values since it's the opposite :'(. $\endgroup$
    – Rebecca
    Mar 9 at 1:40


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