2Electron Configuration - Cations Cations – atoms that lose electrons - metalsElectron Configuration:Magnesium – 12 electrons in its neutral state1s22s22p63s2Magnesium ionLoses 2 electronsNew configuration: 1s22s22p6Notice that the electron configuration is the same as the noble gas NeonThis indicates that by giving 2 electrons away, it obtains an outer octet (stable valence configuration!)
3Electron Configuration - Anions Anions – gain electrons – non-metalsElectron Configuration:Chlorine – 17 electrons in its neutral state1s22s22p63s23p5Chlorine ionGains 1 electronNew configuration: 1s22s22p63s23p6Notice that the electron configuration is the same as the noble gas ArgonThis indicates that by gaining 1 electron, it obtains an outer octet (stable valence configuration!)
4Electron Configuration Both ions obtain a noble gas configurationThis makes the ion and the noble gas isoelectronicIsoelectronic: when two elements and/or ions have the same electronic configurations with one anotherThey tend to have similar chemical properties.
5Isoelectric Examples Li+1 1s2 He 1s2 S-2 1s2 2s2 2p6 3s2 3p6 Ar 1s2 2s2 2p6 3s2 3p6
6Valence ElectronsValence electrons are the outer-most electrons in an atomFor main group elements (Groups 1, 2, 13, 14, 15, 16, 17, 18) they are the highest level s and p electronsExample:Chlorine1s2 2s2 2p6 3s2 3p The 3s and 3p electrons are valence e-
7Valence ElectronsThe d orbital electrons of the transition elements can also be valence electrons, but they are complicated so we will not study themHowever, this is what gives transition elements multiple oxidation statesExample:Manganese: [Ar] 4s23d5 (neutral atom)Possible valence electron configs: 2 to 7!