Trends & the Periodic Table Ionization Energy, Electronegativity, & Metallic Reactivity

Trends More than 20 properties change in a predictable way based on location of element in P.T.More than 20 properties change in a predictable way based on location of element in P.T. Include: density, melting point, atomic radius, ionization energy, electronegativityInclude: density, melting point, atomic radius, ionization energy, electronegativity

Size  as you go  and size  as you go  Source: Conceptual Chemistry by John Suchocki previousprevious | index | nextindexnext

What’s the trend for effective nuclear charge? Effective Nuclear Charge = Atomic # - Inner Shell Electrons. Increases as you go across a row. Stays constant as you go down a column.

Ionization Energy Amount of energy required to remove an electron from a gas-phase atom.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.First ionization energy or ionization energy = energy required to remove most loosely held valence electron. Na(g) + energy  Na +1 (g) + 1e -Na(g) + energy  Na +1 (g) + 1e - (This is an endothermic process!)(This is an endothermic process!)

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

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 previousprevious | index | nextindexnext

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 previousprevious | index | nextindexnext

Trends in ionization energy Ionization energy decreases as you go down a column – it gets easier & easier to remove the valence electron.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.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. Doesn’t have to be a straight line.

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

Formation of a covalent bond Nonpolar Covalent Bond Polar Covalant Bond The green atom is grabbing more than its fair share of the electron cloud. It is more electronegative.

Trends in electronegativity Related to “proton pulling power.”Related to “proton pulling power.” Pulling power depends on size of charge and distance from electrons.Pulling power depends on size of charge and distance from electrons. –What’s the trend for effective nuclear charge? –What’s the trend for atomic size? Increases across. Constant down. Decreases across. Increases down.

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

Reactivity of Metals Metals are losers!Metals are losers! We judge the reactivity of metals by how easily theyelectrons.We judge the reactivity of metals by how easily they give up electrons. What property do we look at to assess how easily metals give up electrons? Ionization energy: the smaller it is, the easier the metal loses electrons.

Reactivity of Metals The most active metals are Cs and Fr. They have the smallest ionization energy.The most active metals are Cs and Fr. They have the smallest ionization energy. For metals, reactivity goes up as ionization energy decreases.For metals, reactivity goes up as ionization energy decreases.

Trends for Reactivity of Metals or Metallic Character Increases as you go down.Increases as you go down. –Easier to lose electrons! Decreases as you go across.Decreases as you go across. –Harder to lose electrons! Can you identify the K, Na, and Li in this clip? Can you identify the K, Na, and Li in this clip?

Reactivity of Non-metals Non-metals are winners!Non-metals are winners! We judge the reactivity of non-metals by how easily theyelectrons.We judge the reactivity of non-metals by how easily they gain electrons. What property do we look at to assess how easily nonmetals gain electrons?What property do we look at to assess how easily nonmetals gain electrons? Electronegativity

Reactivity of Non-metals The most active non-metal is fluorine.The most active non-metal is fluorine. F has the largest electronegativity.F has the largest electronegativity. For non-metals, reactivity increases as electronegativity increases.For non-metals, reactivity increases as electronegativity increases.

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

Allotrope Different forms of an element in the same phase. Have different structures and properties.Different forms of an element in the same phase. Have different structures and properties. O 2 and O 3 - both gas phaseO 2 and O 3 - both gas phase Graphite, diamond, buckey balls – all solid phase carbon.Graphite, diamond, buckey balls – all solid phase carbon.

C 60

Graphite and Diamond