CHE 141 1st Edition Lecture 21 Outline of Current Lecture- Electron Configuration- Oxidation States- D^n Configuration - Lewis Acids and Bases- Complex Ions- Polydentate Ligands - Coordination CompoundsCurrent LectureElectron Configuration- The number of electrons in an atom is equal to its atomic number Z- Ground state the lowest energy configuration - Rules for orbital filling for atomso 1. Electrons fill lower energy orbitals before higher energy orbitalso 2. Hunds rule when orbitals of identical energy are available, electrons first occupy these orbitals singly with parallel spins rather than in pairs o 3. Pauli exclusion principle when two electrons occupy the same orbital their spins are oppositeThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- These three rules are known collectively as the aufbau principle- When writing the electron configuration for elements beyond neon, we abbreviatethe electron configuration - We use the symbol of the noble gas in square brackets to represent the electron configuration of the previous noble gas-this is often called the inner electron configuration- Neon (Ne) has 11 electrons so its configurations is 1s^2 2s^2 2p^6 3s^1- Using inner electron configuration we can abbreviate the electron configuration ofsodium to [Ne]3s^1- In general, ground state electron configurations for 1st row transition metals will have inner electron configuration - The 4s subshell has greater penetration than the 3d subshell, thus electrons in the 4s subshell experience more unclear charge and the 4s subshell is lower in energy than the 3d subshell- When building up according to the aufbau principle, 4s subshells are filled before 3d subshells- Because the 3d and 4s subshells are very close in energy there are two exceptions to the aufbau principle for 1st row transition metals: chromium (Cr) and copper (Cu)- In these cases the lowest energy configurations have half filled or completely filled d subshell- When building up, writing the electron configuration for atoms, you put the 4s in before the 3d- When writing the electronic configurations for cations, losing electrons, remove electrons from 4s subshell before 3d subshellOxidation States- Because of the closeness of the 3d and 4s electron orbitals, transition metals showa wide range of oxidation statesD^n Configuration - Most transition metals lie in the d block, so only have s and d outer electrons- Transition metal cations lose electrons from their outer s subshell before their outer d subshell- The number of outer d electrons if known as the d^n configuration, and these form simple patternsLewis Acids and Bases- Lewis base is a substance that donates a lone pair of electrons in a chemical reaction- Lewis acid is a substance that accepts a lone pair of electrons in a chemical reaction- Lewis definition of a base is consistent with Bronsted Lowry model because a substance must be able to donate a pair of electrons if it is to bond with a H+ ion- Bronsted Lowry model defines an acid as an H+ donor whilst Lewis definition of an acid also encompasses species that have no H+ ions to donate but can still accept electrons, more Lewis acids than Bronsted Lowry acids- Small, highly charged cations form weakly acidic solutionsComplex Ions- A complex ion is an ionic species which is the product of a Lewis acid-base reaction in which neutral molecules or anions (called ligands) bond to a central metal atom by coordinate covalent bonds- Ligand a Lewis base (electron donor) that forms a bond with the central metal ion of a complex ion- Coordinate covalent bond a bond formed when one anion or molecule donates a pair of electrons to another ion or molecule to from a covalent bond- Oxidation state a positive or negative number based on the number of electrons the atom gains or loses when it forms an ion, or that it shares when it forms covalent bond with another element- Coordination number the number of ligands directly bound to the central metal atom- Inner coordination sphere the ligands that are bound directly to a metal via coordinate bondsPolydentate Ligands - Most ligands can only donate one pair of electrons to a metal ion- Even if they have more than one lone pair, the others are oriented away from the metal ion- Monodentate ligand a species that has only one effective donor group thus forms only a single coordinate bond to a metal ion in a complex- Larger molecules may be able to donate more than one lone pair of electrons and thus form more than one coordinate bond to a central metal ion, thus the geometry depends on the denticity of the ligand as well as the number of ligands- Polydenate ligand a species that can form more than one coordinate bond per molecule- Lone pairs on NH2 groups separated from each other by two CH2 groups so ethylenediamine can partially encircle a metal ion such that both lone pairs can bond to a metal ion- The interaction of a metal ion with a ligand having multiple donor atoms is called chelation- The polydenate ligands that take part in these interactions are called chelating agents- Chelating agents can have more than one kind of electron pair-donating group- Ethylenediaminetraacetate has six donor groups: two amine groups and four carboxylic acid groupsCoordination Compounds- Counterion ions of opposite charge that are not acting as ligands- When a comlex ion combines with one or more counterions, the resulting neutral compound is called a coordination