Electron affinity cont
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Electron affinity cont. As e- add to the same p sublevel of atoms with increasing nuclear charge. E- affinities become more negative across each period within the p block. Exception between groups 14 and 15

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Electron affinity cont.

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Electron affinity cont

Electron affinity cont.

  • As e- add to the same p sublevel of atoms with increasing nuclear charge.

  • E- affinities become more negative across each period within the p block.

  • Exception between groups 14 and 15

  • Adding an e- to a carbon atom gives a half-filled p sublevel, this occurs more easily than forcing an e- to pair with another e- in an orbital of the already half-filled


Group trends

Group trends

  • E- add with greater difficulty down a group.

  • Because of an increase in effective nuclear charge down a group, which increases e- affinity.

  • Increase in atomic radius down a group, decreases e- affinities.

  • Exception – heavy transition metals, tend to be the same size or even decrease in radius down a group.


Adding e to negative ions

Adding e- to negative ions

  • For an isolate ion in the gas phase, it is always more difficult to add a second e- to an already negatively charged ion.

  • Second e- affinities are all positive.

  • Certain p-block nonmetals tend to form negative ions that have noble gas configurations.

  • With halogens it is difficult to add another e- because they have noble gas configuration after becoming a negative one ion.


Ionic radii

Ionic radii

  • Cation – positive ion, loss of one or more electrons. – leads to decrease in atomic radius

  • Anion – negative ion, addition of one or more e-, leads to an increase in atomic radius. (positive charge remains the same)


Period trends

Period trends

  • Metals tend to form cations.

  • Nonmetals at the upper right tend to form anions.

  • Cationic radii decrease across a period because the e- cloud shrinks due to the increasing nuclear charge acting on the e-.

  • Anionic radii decrease across each period for the elements in groups 15-18. (same reason why cation radius decrease)


Valence electrons

Valence electrons

  • Electrons available to be lost, gained, or shared in the formation of chemical compounds.

  • Usually located in incompletely filled main-energy levels.

  • What sublevel are the valence e- located?

  • Group 1 and 2

  • Transition elements

  • Group 13-18


Electronegativity

electronegativity

  • Linus Pauling devised a scale of numerical values reflecting the tendency of an atom to attract electrons.

  • Electronegativity – measure of the ability of an atom in a chemical compound to attract e- from another atom in the compound.

  • Most electronegative element is Flourine

  • Why not At?


Period trends1

Period trends

  • Electronegativities tend to increase across each period

  • alkali and alkaline-earth metals are the least electronegative.


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