Electron Configuration: Ions Valence Electrons

Electron Configuration - Cations Cations – atoms that lose electrons - metals Electron Configuration: Magnesium – 12 electrons in its neutral state 1s22s22p63s2 Magnesium ion Loses 2 electrons New configuration: 1s22s22p6 Notice that the electron configuration is the same as the noble gas Neon This indicates that by giving 2 electrons away, it obtains an outer octet (stable valence configuration!)

Electron Configuration - Anions Anions – gain electrons – non-metals Electron Configuration: Chlorine – 17 electrons in its neutral state 1s22s22p63s23p5 Chlorine ion Gains 1 electron New configuration: 1s22s22p63s23p6 Notice that the electron configuration is the same as the noble gas Argon This indicates that by gaining 1 electron, it obtains an outer octet (stable valence configuration!)

Electron Configuration Both ions obtain a noble gas configuration This makes the ion and the noble gas isoelectronic Isoelectronic: when two elements and/or ions have the same electronic configurations with one another They tend to have similar chemical properties.

Isoelectric Examples Li+1 1s2 He 1s2 S-2 1s2 2s2 2p6 3s2 3p6 Ar 1s2 2s2 2p6 3s2 3p6 

Valence Electrons Valence electrons are the outer-most electrons in an atom For main group elements (Groups 1, 2, 13, 14, 15, 16, 17, 18) they are the highest level s and p electrons Example: Chlorine 1s2 2s2 2p6 3s2 3p5 - The 3s and 3p electrons are valence e-

Valence Electrons The d orbital electrons of the transition elements can also be valence electrons, but they are complicated so we will not study them However, this is what gives transition elements multiple oxidation states Example: Manganese: [Ar] 4s23d5 (neutral atom) Possible valence electron configs: 2 to 7!