PS Weiss

1
Recap of Lecture 10 Periodic Trends
Periodic Trends Know which direction across the
periodic table determines property. Ionization
Energy ? Low if resulting ion has filled shell
rare gas configuration. (or to a lesser extent
-- has filled or half-filled subshells) Same
rules for higher oxidation states (e.g.
Mg2). Electron Affinitites ? (Negative values
for species with stable anions.) Related to
electronegativity ? -- many ways to define
this. Determine dipoles within molecules. Atomic
Ionic Sizes ? Size decreases with more positive
oxidation state for isoelectronic atoms/ions.
2
Recap of Lecture 10 Periodic Trends, cont.
Metals To left of periodic table. Form
cations. Consider prototypical Na -- e.g. basic
oxides, hydrides and hydroxides. Non-metals To
right of periodic table. Form anions or covalent
compounds. Consider prototypical Cl -- e.g.
acidic oxides and hydroxides. Acidic (when more
to the right) or neutral hydrides. Ionic
compounds and solids Consider Coulombs Law E?
Q1Q2/r Melting point and boiling measure cohesive
energies.