CHEM 131 Lecture Notes - Lecture 5: Valence Electron, Noble Gas, Nonmetal

• School: University of Maryland
• Department: Chemistry and Biochemistry
• Course: CHEM 131
• Professor: John Ondov

Document Summary

Valence electrons: electrons involved in boding, s block- valence electrons always ns1/ns2, outside the previous noble gas core, ex. Mg- group 2a (ne) 3s2: period 4- for p and d blocks- n-1d electrons, valence electrons if the n-1d/f orbitals partially filled. Effective nuclear charge: inner shield outer from charge on nucleus, zeff=z-number of core electrons, ex. Metals: lose electrons easily: positive cations, shiny, conductive, solids: soft, ductile, nuclei sea of electrons, react with nonmetals. Nonmetals: gain electrons: anions, dull, poor conductors, for molecular and ionic solids: hard, brittle. Metalloids: metallic character increases down and to right on periodic table, have metallic behavior. Transition elements fill in order of ns before n-1d. But once filled the fields of the n-1 d electrons perturb the ns and repel the to a higher energy. Electrons in n-1d rbitals are closer to the nucleus than ns.