Ionization energy

• ionization energy (IE) (אנרגיית יינון)
  • the minimum energy required to remove an electron from the ground state of the isolated gaseous atom or ion
• 1st ionization energy ($I_1$): $\mathrm{X}(\mathrm{g})+\mathrm{energy}\to \mathrm{X}{}^{+}(\mathrm{g})+\mathrm{e}{}^{-}$
• 2nd ionization energy ($I_2$): $\mathrm{X}{}^{+}(\mathrm{g})+\mathrm{energy}\to \mathrm{X}{}^{2+}(\mathrm{g})+\mathrm{e}{}^{-}$
• 3rd ionization energy ($I_3$): $\mathrm{X}{}^{2+}(\mathrm{g})+\mathrm{energy}\to \mathrm{X}{}^{3+}(\mathrm{g})+\mathrm{e}{}^{-}$
• $I_1<I_2<I_3<\dots$
• removing core electrons requires significantly higher IE then removing valence electrons
• periodic trends for $I_1$:
  • higher $I_1$ for higher groups
  • lower $I_1$ for higher periods
• unit: $kJ/mol$, $\mathrm{eV}$

Electron affinity

• electron affinity ($E_{\text{ea}}$) (זיקת-אלקטרונים, זיקה אלקטרונית)
  • $\mathrm{X}(\mathrm{g})+\mathrm{e}{}^{-}\to \mathrm{X}{}^{-}(\mathrm{g})+\mathrm{energy}$
  • unit: $kJ/mol$, $\mathrm{eV}$
  • $E_{\text{ea}}>0$, energy released, stable anion formed, when electron attachment is exothermic ($\Delta E<0$)
  • $E_{\text{ea}}\approx 0\text{ or negative}$, electron attachment is not favorable, electron attachment is endothermic ($\Delta E>0$)
  • $E_{\text{ea}}=E(\mathrm{X})+E(\mathrm{e}{}^{-})-E(\mathrm{X}{}^{-})=-\Delta E$
  • Lowest for noble gases and alkali metals
  • Highest for halogens