To understand the principle of electron affinity as a measure of the power required to include an electron come an atom or ion. To acknowledge the inverse relationship of ionization energies and also electron affinities

The electron affinity ($$EA$$) that an aspect $$E$$ is characterized as the energy change that occurs once an electron is included to a gaseous atom or ion:

\< E_(g)+e^- \rightarrow E^-_(g) \;\;\;  \textenergy change=EA \label7.5.1\>

Unlike ionization energies, which are always positive for a neutral atom because energy is compelled to remove an electron, electron affinities can be an adverse (energy is released as soon as an electron is added), hopeful (energy should be added to the device to develop an anion), or zero (the process is energetically neutral). This sign convention is constant with a negative value synchronized to the energy readjust for an exothermic process, which is one in which warmth is released (Figure $$\PageIndex1$$).

You are watching: Which element has the highest most negative electron affinity Figure $$\PageIndex1$$: A Plot of regular Variation that Electron Affinity with Atomic Number for the very first Six Rows of the regular Table. Notification that electron affinities deserve to be both an adverse and positive. Native Robert J. Lancashire (University of the West Indies).

The chlorine atom has actually the most an unfavorable electron affinity of any type of element, which means that more energy is released when an electron is added to a gaseous chlorine atom 보다 to one atom of any type of other element:

\< \ce Cl(g) + e^- \rightarrow Cl^- (g) \;\;\;  EA=-346\; kJ/mol \label7.5.2\>

In contrast, beryllium walk not form a stable anion, so its efficient electron affinity is

\< \ce Be(g) + e^- \rightarrow Be^- (g) \;\;\;  EA \ge 0 \label7.5.3\>

Nitrogen is unique in the it has an electron affinity of roughly zero. Including an electron no releases nor calls for a far-reaching amount the energy:

\< \ce N(g) + e^- \rightarrow N^- (g) \;\;\;  EA \approx 0 \label7.5.4\>

Generally, electron six become more negative throughout a heat of the regular table.

In general, electron affinities of the main-group facets become less an adverse as we continue down a column. This is because as n increases, the extra electrons enter orbitals that space increasingly much from the nucleus. Figure $$\PageIndex2$$: Electron affinities (in kJ/mol) the the s-, p-, and d-Block Elements.

Atoms with the largest radii, which have the lowest ionization energies (affinity because that their own valence electrons), additionally have the shortest affinity for an included electron. There are, however, two major exceptions to this trend:

The electron six of elements B through F in the second row the the regular table space less negative than those the the aspects immediately below them in the 3rd row. Apparently, the increased electron–electron repulsions skilled by electron confined to the relatively small 2p orbitals overcome the boosted electron–nucleus attraction at brief nuclear distances. Fluorine, therefore, has actually a reduced affinity for an added electron 보다 does chlorine. Consequently, the facets of the third row (n = 3) have the most negative electron affinities. Farther under a column, the attraction for an included electron decreases due to the fact that the electron is beginning an orbital an ext distant indigenous the nucleus. Electron–electron repulsions likewise decrease because the valence electrons occupy a higher volume that space. These impacts tend to cancel one another, so the transforms in electron affinity within a family are much smaller 보다 the transforms in ionization energy. The electron affinities of the alkaline planet metals become more negative from it is in to Ba. The power separation between the fill ns2 and the north np subshells reduce with raising n, so that development of an anion from the heavier aspects becomes energetically more favorable.[Image_Link]https://positiveeast.org/

Example $$\PageIndex1$$: difference Electron six of Sb, Se, and Te

Based on their positions in the routine table, i beg your pardon of Sb, Se, or Te would certainly you predict to have actually the most negative electron affinity?

Given: three elements

Asked for: element with most negative electron affinity

Strategy:

situate the aspects in the routine table. Use the patterns in electron affinities going down a pillar for elements in the same group. Similarly, use the patterns in electron affinities from left to right for elements in the very same row. Ar the facets in order, listing the element with the most negative electron affinity first.

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Solution:

A We recognize that electron affinities come to be less an unfavorable going down a tower (except for the anomalously short electron six of the elements of the second row), therefore we deserve to predict the the electron affinity of Se is much more negative 보다 that of Te. We likewise know the electron affinities become much more negative native left come right throughout a row, and also that the team 15 facets tend to have actually values that room less negative than expected. Because Sb is situated to the left the Te and also belongs to group 15, us predict that the electron affinity of Te is an ext negative than that of Sb. The all at once order is Se practice $$\PageIndex1$$: contrasting Electron affinities of Rb, Sr, and also Xe

Based on their positions in the routine table, i m sorry of Rb, Sr, or Xe would certainly you guess to most likely kind a gas anion?