Chemical Periodicity? What?

Periodicity When elements are organized in order of  atomic mass, and grouped by similarities of chemical properties, a certain “pattern” or periodicity of properties becomes evident Draft for first version of Mendeleev's periodic table (17 February 1869).

Review of the Periodic Table

Review of the Periodic Table Group IA – alkali metals Review of the Periodic Table

Group IA – alkali metals H1 - 1s1 Li3 - 1s22s1 Na11 - 1s22s22p63s1 K19 - 1s22s22p63s23p64s1 Rb37 - 1s22s22p63s23p63d104s24p65s1 Cs55 - 1s22s22p63s23p63d104s24p64d105s25p66s1 Fr87 - 1s22s22p63s23p63d104s24p64d104f145s25p65 d106s26p67s1

Review of the Periodic Table Group IIA – alkaline earth metals Review of the Periodic Table

Group IIA – alkaline earth metals Be4 - 1s2 2s2 Mg12 - 1s22s22p63s2 Ca20 - 1s22s22p63s23p64s2 Rb38 - 1s22s22p63s23p63d104s24p65s2 Cs55 - 1s22s22p63s23p63d104s24p64d105s25p66s2 Fr87 - 1s22s22p63s23p63d104s24p64d104f145s25p65 d106s26p67s2

Review of the Periodic Table Group VIII – Noble Gases Review of the Periodic Table

Group VIII – Noble Gases He2 - 1s2 Ne10 - 1s22s22p6 Ar18 - 1s22s22p63s23p6 Kr36 - 1s22s22p63s23p63d104s24p6 Cs54 - 1s22s22p63s23p63d104s24p64d105s25p6 Rn86 - 1s22s22p63s23p63d104s24p64d104f145s25p65 d106s26p6

Review of the Periodic Table Group VII – Halogens Review of the Periodic Table

Group VII – Halogens F9 - 1s22s22p5 Cl17 - 1s22s22p63s23p5 Br35 - 1s22s22p63s23p63d104s24p5 I53 - 1s22s22p63s23p63d104s24p64d105s25p5 At85 - 1s22s22p63s23p63d104s24p64d104f145s25p65 d106s26p5

Review of the Periodic Table Group VI

Group VI O8 - 1s22s22p4 S16 - 1s22s22p63s23p4 Se34 - 1s22s22p63s23p63d104s24p4 Te52 - 1s22s22p63s23p63d104s24p64d105s25p4 Po84 - 1s22s22p63s23p63d104s24p64d104f145s25p65 d106s26p4

Electron’s Role in Chemical Behavior Atoms are most stable when their outermost “s” and “p” subshells are filled. – “the rule of 8” Electron’s in the outermost shell determine chemical reactivity

Periodic Table and e- config. 1 2 3 4 5 6 7 Increasing energy level (shell) px1 py1 pz1 px2 py2 pz2 s1 s2 Increasing energy sublevel (subshell)

Periodic Patterns - Atomic Radii

Atomic Radii

Periodicity and Atomic Radius In group: atomic radius increases as you move down the column Across period: Atomic radius decreases as you Move from left to right Rationale: group – adding outermost electron shell row –  pulling in with  nuclear charge

Ionic Radius 97pm vs 181pm 190pm vs 102pm

Periodic Patterns and Ionic Radius In group: ionic radius increases as you move down the column Across period: Ionic radius is max in group 5 Lower on left and right Rationale: group –outermost shell row – transition between losing and gaining electrons to reach stability

Ionic Radius

Periodic Patterns and Ionization Energy Ionization energy ≡ energy needed to remove an electron from an atom or ion first ionization energy - energy needed to remove an electron from a neutral atom second ionization energy - energy needed to remove a second electron from a positively charged ion

Ionization Energy

Periodic Patterns and Ionization Energy In group: ionization energy  as you move down the column Across period: Ionization energy  as you move from left to right Rationale: group –outermost shell electrons farther away from nucleus row – outermost electron more tightly held

Ionization Energy

Periodicity and Electronegativity Electronegativity ≡ a measure of how tightly held an electron is.

Electronegativity

Periodicity and Electronegativity In group: electronegativity  as you move down the column Across period: Electronegativity  as you move from left to right Rationale: group –atoms more willing to accept another electrons due to  nuclear charge and shielding row – atoms move closer to completed “s” and “p” orbitals and stability

Electronegativity

Periodic Trends – Summary Decreasing Atomic Radii Decreasing Ionic Size Increasing Ionization Energy Increasing Electronegativity Decreasing Ionization Energy Decreasing Electronegativity Increasing Atomic Radii Increasing Ionic Radius