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 2p63s2 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!