Electron AffinityElectron Affinity

By: Victoria Geissler, Nichole By: Victoria Geissler, Nichole Hollon, Daniel Rosenberg, and Hollon, Daniel Rosenberg, and

Ben SchlechterBen Schlechter

DefinitionDefinition of Electron of Electron Affinity Affinity

• Electron Affinity is when the Electron Affinity is when the energy is absorbed in the energy is absorbed in the process in which an electron is process in which an electron is added to a neutral isolated added to a neutral isolated gaseous atom to form a gaseous gaseous atom to form a gaseous ion with a one charge and has a ion with a one charge and has a negative value if energy is negative value if energy is released.released. This is kind of like This is kind of like gravity.gravity.

ConceptConcept

• Electrons as said in the previous Electrons as said in the previous slide is the different amounts of slide is the different amounts of energy that is absorbed when an energy that is absorbed when an electron is added to an neutral cut electron is added to an neutral cut off gaseous atom to create a off gaseous atom to create a gaseous ion (an ion is an atom or a gaseous ion (an ion is an atom or a group of atoms that carries an group of atoms that carries an electric charge) with a charge. In electric charge) with a charge. In other words the energy is released. other words the energy is released.

Electron ConfigurationsElectron Configurations

This graph shows the behavior of the electron affinity.

The shell of the most bound vacancy is indicated by its

spectroscopic designation.

Effective Nuclear ChargeEffective Nuclear Charge

• The effective nuclear charge, The effective nuclear charge, ZeffZeff, is the amount of positive , is the amount of positive charge on the nucleus perceived charge on the nucleus perceived by an electron. by an electron.

• Electrons intervening between Electrons intervening between the nucleus and an outer electron the nucleus and an outer electron are said to shield or screen the are said to shield or screen the outer electron from the nucleus outer electron from the nucleus so that the outer electron does so that the outer electron does not experience the full nuclear not experience the full nuclear charge.charge.

Periodic Trends of Periodic Trends of Electron AffinityElectron Affinity

• The electron affinity is a measure of the The electron affinity is a measure of the energy change when an electron is added to a energy change when an electron is added to a neutral atom to form a negative ion. For neutral atom to form a negative ion. For example, when a neutral chlorine atom in the example, when a neutral chlorine atom in the gaseous form picks up an electron to form a gaseous form picks up an electron to form a Cl- ion, it releases energy of 349 kJ/mol or 3.6 Cl- ion, it releases energy of 349 kJ/mol or 3.6 eV/atom. It is said to have an electron affinity eV/atom. It is said to have an electron affinity of -349 kJ/mol and this large number indicates of -349 kJ/mol and this large number indicates that it forms a stable negative ion. Small that it forms a stable negative ion. Small numbers indicate that a less stable negative numbers indicate that a less stable negative ion is formed. Groups VIA and VIIA in the ion is formed. Groups VIA and VIIA in the periodic table have the largest electron periodic table have the largest electron affinities.affinities.

Periodic TrendsPeriodic Trends

• Ionization energies are always concerned with the Ionization energies are always concerned with the formation of positive ions. Electron affinities are the formation of positive ions. Electron affinities are the negative ion equivalent, and their use is almost negative ion equivalent, and their use is almost always confined to elements in groups 6 and 7 of the always confined to elements in groups 6 and 7 of the Periodic Table.Periodic Table.

• In electron affinity the energy is released when a In electron affinity the energy is released when a single electron is combined with an isolated atom; single electron is combined with an isolated atom; its value is determined by the effective charge on its value is determined by the effective charge on the nucleus and the size and electronic configuration the nucleus and the size and electronic configuration of the atom. The energy change accompanying the of the atom. The energy change accompanying the addition of an electron to a species. The energy addition of an electron to a species. The energy given off when a neutral atom in the gas phase picks given off when a neutral atom in the gas phase picks up an electron to form a negatively charged ion. up an electron to form a negatively charged ion.

BibliographyBibliography• http://www.http://www.chemguidechemguide.co..co.ukuk/atoms/properties//atoms/properties/easeas.html.html• http://http://hyperphysicshyperphysics..phyphy--astrastr..gsugsu..eduedu//hbasehbase/chemical//chemical/eleaffeleaff

.html.html• http://www.http://www.iuniun..eduedu/~/~cpanhdcpanhd

/C101webnotes/modern-atomic-theory/electron-affinity.html/C101webnotes/modern-atomic-theory/electron-affinity.html • http://www.http://www.britannicabritannica.com/.com/ebeb

/article-9032317/electron-affinity/article-9032317/electron-affinity • http://www.http://www.chemguidechemguide.co..co.ukuk/atoms/properties//atoms/properties/easeas.html.html • www.www.mercksourcemercksource.com/pp/us/.com/pp/us/cnscns//cnscns_hl__hl_dorlandsdorlands..

jspzQzpgzEzzSzppdocszSzuszSzcommonzSzdorlandszSzdorljspzQzpgzEzzSzppdocszSzuszSzcommonzSzdorlandszSzdorlandzSzdmdandzSzdmd_a_18zPzhtm_a_18zPzhtm

• www.everyscience.com/Chemistry/Glossary/E.phpwww.everyscience.com/Chemistry/Glossary/E.php • xenon.che.ilstu.edu/genchemhelphomepage/xenon.che.ilstu.edu/genchemhelphomepage/

glossary/e.htmlglossary/e.html • en.wikipedia.org/wiki/Electron_affinityen.wikipedia.org/wiki/Electron_affinity