# Lecture 13: Electron Configurations

• ﻿$S$﻿ block elements
• ﻿$P$﻿ block elements
• ﻿$d$﻿ block elements ﻿$\rightarrow$﻿ Transition Metals
• ﻿$f$﻿ block elements ﻿$\rightarrow$﻿ Lanthanides (﻿$4f$﻿) and Actinides (﻿$5f$﻿)
• Metaloids - Show properties of metals and non-metals
• Transition Metals - Electrons are removed from the highest energy shell

• How many impaired electrons?
• ﻿$4S$﻿ is lower energy than ﻿$3d$﻿, but once ﻿$4S$﻿ is full it is higher energy from ﻿$3d$﻿
• Electrons are always removed from the highest energy
• What is the electron configuration of ﻿$Mn^{4+}$﻿ ?
• ﻿$1S^2 2S^2 Sp^6 3S^2 3p^6 4S^2 3d^3$﻿ or ﻿$1S^2 2S^2 2p^6 3S^2 3p^6 3d^3$﻿

• Isoelectronic Series - All the species with the same number of electrons
• Orbital Penetration - ﻿$S>P>d>f$﻿
• Shield Effect - Effective nuclear charge
• The positive charge that an electron actually experiences, ﻿$Z_{eff}$﻿ and this is always somewhat less than the actual than the nuclear charge
• ﻿$Z_{eff}$﻿ = ﻿$2 - s$﻿ (﻿$s$﻿ - shielding constant)
• Penetration of Orbitals - An electron in an ﻿$s$﻿ orbital has a finite, albeit very small probability of being located quite close to the nucleus
• The ﻿$s$﻿ orbital is more penetrated than ﻿$p$﻿ or ﻿$d$﻿, meaning than an electron is an ﻿$s$﻿ orbital that has a greater chance of being located close to the nucleus than an electron in a ﻿$p$﻿ or ﻿$d$﻿ orbital