Electron affinities

Example that IE1 that Magnesium: Mg(g) -> Mg+(g) + e- I1 = 738 kJ/mol

IE1 stands for the first ionization energy: the energy the atom requires to expel the an initial electron native its orbital. Similarly, the 2nd ionization energy, will be the power needed come expel the 2nd electron.

Mg+(g) -> Mg2+(g) + e- I2 = 1,451 kJ/mol

However, IE2 the Magnesium will be bigger than the of IE1 because it is not energetically favorable to separate an electron indigenous a positively charged ion.

The general pattern of the ionization energy as they room in regard come the duration table is the the in other words increases throughout a period, and decreases under a group. Due to the fact that it requires much more energy to eliminate an electron indigenous a steady atom, the noble gases are usually connected with the highest IE1. Because their valence shells are already filled and stablized, lock will require much much more energy come disrupt that stability. The very first electron the is expelled is the most loosely organized to the atom.

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On the various other hand, the team 1 elements are usually associated with the lowest IE1. Due to the fact that only one electron rectal the valence shell of these atoms, it will certainly be an ext energetically favorable for them to shed the electron in stimulate to attain a complete orbital shell.

However, there are couple of exceptions. The IE1 decreases when crossing from element in team 15 come the element in group 16. The team 15 has half-filled digital configuration ns2 np3. This kind of configuration is really stable; it’s hard to remove electron from valence shell. Therefore, element in group 15 requires greater value the IE1 than team 16. One more exception is the going from it is in (group 2) to B (group 13), the IE1 decreases since Be has the filled shell 2s2 which is more stable than the electronic configuration the B 2s2 2p1. Hence, Be will certainly require more IE1 than B. Similarly, the IE1 decreases as soon as going from elements in group 12 to group 13


Electron Affinities

Electron affinity, often abbreviated as EA, is the energy released once an electron is added to a valence covering of the atom.

F(g) + e- -> F-(g) EA = -328 kJ/mol

Atoms like the noble gases will certainly not obtain an electron due to the fact that they are already in their many stable state v a complete shell. Atoms favor F will most likely get an electron because when a complimentary electron is included to the outer shell of fluorine, it will have acquired a full shell. Generally, atoms increasing across a period will increase in EA also.

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Exothermic vs endothermic process

O(g) + e- -> O-(g) EA1= -141.0 kJ/mol

O-(g) + e- -> O2-(g) EA2 = +744kJ/mol

When one electron is added to an atom, the energy adjust is exothermic since of the attraction the the electron to the nucleus. However, in the situation of EA2 where the electron is included to an anion, the repulsion between the anion and also this newly included electron will certainly overwhelm the attraction that the electron to the nucleus. Therefore, this process will be endothermic, as opposed to EA1.


Periodic Trend

The basic trend of IE and also EA follow me a routine table.

IE and also EA.jpgrelationship between ionization energy and electron affinity