CHM 113 Lecture Notes - Core Electron, Fluorine, Electron Configuration
Document Summary
Valence electrons (ve): an electron that resides in outermost shell of an atom. Fluorine (9e-): 1s22s22p5: 1s2: n=1, 2s22p5: n=2, 7 ve"s. Number of ve equals group number on periodic table: halogens: 7 ve, o, s, etc: 6 ve, alkaline medals (na, k): 1 ve, noble gases: 8 ve (except he, which has 2) [ne] 3s2: 2 ve (n=3, 10 core electrons, 12 protons in nucleus. Electrons attracted by protons in nucleus (but not all equally) Ve are shielded from nucleus by core electrons. Ve are shielded from nucleus by other ve (only weakly) Zeff: net positive charge that an electron sees from the nucleus: zeff = z s, z represents number of protons in nucleus, s represents the number of shield (core) electrons. Trends in zeff experienced by ves: as you go from left to right on a row, zeff increases.