Trends & the Periodic Table

Ionization Energy Amount of energy required to remove an electron from a gas-phase atom First ionization energy or ionization energy = energy required to remove most loosely held valence electron

Trends in ionization energy What do you think happens to the ionization energy as you go down a column of the periodic table? As you go across a row?

 previous | index | next                                                                                                                                                                                                                    Valence electrons in both atoms feel an effective nuclear charge of +1, but the Cs valence electron is a lot farther away from the nucleus The electrostatic attraction will be much weaker so it’s easier to steal the electron away from Cs Source: Conceptual Chemistry by John Suchocki

 It’s easier to steal an electron from the Li than the Ne previous | index | next                                                                                                                                                                                                                    It’s easier to steal an electron from the Li than the Ne Li has a smaller effective nuclear charge and the valence electron is a little farther away from the nucleus Li has less “proton pulling power” than Ne Source: Conceptual Chemistry by John Suchocki

Trends in ionization energy Ionization energy decreases as you go down a column it gets easier & easier to remove the valence electron Ionization energy increases as you go across a row it gets more difficult to remove the valence electron

Periodic properties: Graph shows a repetitive pattern (Note: Doesn’t have to be a straight line)

Electronegativity Relative ability of an atom to attract electrons in a bond The noble gases tend not to form bonds, so they don’t have electronegativities Unit = Pauling Fluorine is the most electronegative element at 4.0 Paulings

Trends in electronegativity Related to “proton pulling power” Increases as you go across a row Decreases as you go down a column Remember: F is the most electronegative element!

Reactivity of Metals Metals are losers! We judge the reactivity of metals by how easily they give up electrons The most active metals are Cs and Fr For metals, reactivity goes up as ionization energy goes down

Trends for Reactivity of Metals or Metallic Character Increases as you go down Easier to lose electrons! Decreases as you go across Harder to lose electrons!

Reactivity of Non-metals Non-metals are winners! We judge the reactivity of non-metals by how easily they gain electrons The most active non-metal is fluorine For non-metals, reactivity increases as electronegativity increases

Trend for Reactivity of Non-metals: Depends on “proton pulling power” Increases as you go across Decreases as you go down (Shielded by more inner-shell electrons)