Periodic Trends Atomic radii Ionization Energy Multiple Ionization

  • Slides: 9
Download presentation
Periodic Trends Atomic radii Ionization Energy Multiple Ionization Energy Electron Affinity Electronegativity

Periodic Trends Atomic radii Ionization Energy Multiple Ionization Energy Electron Affinity Electronegativity

Atomic Radius l l l Is an estimate of the size of an atom

Atomic Radius l l l Is an estimate of the size of an atom from its nucleus to its outer perimeter (measured in pm or 10 -12 m) Trend: Increases to the left and down Reason: core charge increases across the period pulling electrons closer in and added shells increase distance and decrease pull

Ionization energy l l The energy needed to remove an electron from the gaseous

Ionization energy l l The energy needed to remove an electron from the gaseous atom. 1 st ionization energy removes electron with the smallest amount of attraction to the nucleus The atom become a positive ion- cation when it loses an electron Ionization energy is measured in MJ/mol

Ionization energy (cont) l Trend: Ionization energy increases as you go right and up

Ionization energy (cont) l Trend: Ionization energy increases as you go right and up l Reason: atomic radius decreases, electrons are pulled in by greater nuclear charge l Reason: atomic radius increases, pull by far away nucleus decreases as well as screening makes it easier to remove an electron

Electron Affinity l l Electron affinity is the energy released when an electron is

Electron Affinity l l Electron affinity is the energy released when an electron is added to a gaseous atom (measured in k. J/mol). The atom becomes a negative ion (anion) when it accepts an electron Trend: Electron affinity increases as you go right and up. Reason: Across a period, radius decreases, atomic charge increases, greater pull.

Electron affinity (cont) l l Trend: As you go down a group, electron affinity

Electron affinity (cont) l l Trend: As you go down a group, electron affinity decreases Reason: Greater radius, decreased nuclear pull and electrons circling in far orbits make adding an electron not as desirable

Electronegativity l l Property that determines the relative strength of attraction by an atom

Electronegativity l l Property that determines the relative strength of attraction by an atom of a bonding electron pair in a chemical compound F-F equal sharing of electrons in the covalent bond. H-F unequal sharing of electrons. Fluorine has a greater attraction and electrons stay closer to fluorine than hydrogen in the covalent compound.

Electronegativity (cont) l l Trend: Increases across a period Reason: core charge Trend: Decreases

Electronegativity (cont) l l Trend: Increases across a period Reason: core charge Trend: Decreases as you go down a group Reason: far orbits have a decreased attraction to far away nucleus

Multiple Ionization energy l l l Every electron can be successively removed from an

Multiple Ionization energy l l l Every electron can be successively removed from an atom- 1 st, 2 nd, 3 rd… ionization energy At each successive removal, ionization energy increases Trends are consistent with 1 st ionization energy and the model of the atom