Acid Base Character of period 3

The Period 3 Oxides Element Formula of oxide Reaction of oxide with water Acid/base nature Sodium Na2O Na2O + H2O  2NaOH Strongly basic Magnesium MgO Slight: MgO + H2O  Mg(OH)2 Weakly basic Aluminium Al2O3 Amphoteric Silicon SiO2 Very weakly acidic Phosphorous P4O10 P4O10 + 6 H2O  4 H3PO4 Strongly acidic Sulphur SO2 SO3 SO3 + H2O  H2SO4 Chlorine no direct reaction but: Cl2O7 Cl2O7 + H2O  2 HClO4 Argon no oxides There is a gradual transition from basic to acidic character, reflecting a gradual transition from metallic to non-metallic nature

Lesson 6 Transition Metal Complexes - Introduction

Lesson 6: Transition Metal Complexes -Introduction Objectives: Describe the properties of transition metals Understand the term ligands Understand and explain the formation of transition metal complexes

The Traditional Based on Mendeleev’s work. Easiest to use and display.

The Transition Metals A transition metal is an element in which at least one ion has a partially filled d-orbital For example, Cu2+: 1s2 2s2 2p6 3s2 3p6 (4s0) 3d9 Properties of the transition metals include: Variable oxidation states (for example iron: Fe2+, Fe3+, Fe6+) Formation of coloured compounds Catalytic properties Formation of complex ions

Scandium and Zinc Although in the first row of the d-block, these are not transition metals. To understand why, write the full electron configuration for: Sc and Sc3+ Zn and Zn2+

Variable oxidation numbers (ions) Transition metals have large numbers of electrons in d- orbitals, This means the amount of energy required to remove the second electron is not much different to that required to remove the first and so on. Some common oxidation states we need to know: All of them in the +2 oxidation state Cr(III), Cr(VI) Mn(IV), Mn(VII) Fe(III) Cu(II)

Formation of complex ions Ligands:

Ligands A ligand is a species with a lone pair Common ligands include: Often negative ions Common ligands include: Water, H2O Ammonia, NH3 Chloride, Cl- Hydroxide, OH- Cyanide, CN- Thiocyanate, SCN-

Transition Metal Complexes The lone pair on a ligand can form a dative covalent bond to a metal ion to form a transition metal complex. This involves the ligands donating charge into the empty 4d and 4s orbitals (at least for the first-row of transition elements), not the partially occupied 3d orbitals. [Fe(H2O)6]3+ [Fe(CN)6]3- [Cu(Cl)4]2- [Ag(NH3)2]+

Complex Ions Transition metal ions in solution have a high charge density and attract water molecules to from coordinate bonds with the positive ions to form complex ions.

Formation of complex ions The electron pair from a ligand can form coordinate covalent bonds with the metal ion to form complex ions. A “coordinate covalent bond” is also known as a “dative” - a bond in which both shared electrons are supplied by one species. ligand coordinate covalent bond

Formation of complex ions Coordination number: the number of lone pairs bonded to the metal ion. L: :L Mn+ Shape: linear Coordination # = 2

Formation of complex ions Coordination number: the number of lone pairs bonded to the metal ion. L: :L Mn+ :L L: Shape: square planar Coordination # = 4

Formation of complex ions Coordination number: the number of lone pairs bonded to the metal ion. L .. Shape: tetrahedral Coordination # = 4 Mn+ L: :L .. L

Formation of complex ions Coordination number: the number of lone pairs bonded to the metal ion. L .. L: :L Shape: octahedral Coordination # = 6 Mn+ L: :L .. L

Coordination number: the number of lone pairs bonded to the metal ion. Examples: state the coordination numbers of the species below. [Fe(CN)6]3- [CuCl4]2- [Ag(NH3)2]+ 6 4 2

Colored Complexes

Big Ideas The d-sublevel splits into two sets of orbitals of different energy in a complex ion Complexes of the d-orbital are colored, as light is absorbed when an electron is excited between d orbitals The color absorbed is complimentary to the color shown.

Transition Metal Colour Chart Configuration Colour Sc3+ [Ar] None Ti3+ [Ar]3d1 Violet V3+ [Ar]3d2 Green Cr3+ [Ar]3d3 Mn2+ [Ar]3d4 Pink Fe3+ [Ar]3d5 Yellow Fe2+ [Ar]3d6 Co2+ [Ar]3d7 Ni2+ [Ar]3d8 Cu2+ [Ar]3d9 Blue Zn2+ [Ar]3d10 Colourless

Both are “clear.” Only the beaker on the left is “colorless.” Colored Complexes NOTE: it is important to distinguish between the words “clear” and “colorless.” Neither AP, nor IB, will give credit for use of the word clear (which means translucent) when colorless should have been used. Think about it, something can be pink and clear… colorless means something else. Both are “clear.” Only the beaker on the left is “colorless.”

Visible Light Spectrum

Colour depends on two things overall. The strength of the coordinate bond between the ligand and the central metal ion. Ligands interact more effectively with the d-orbitals of ions with higher nuclear charge.

For Example [Mn(H2O)6]2+ and [Fe(H20)6]3+ Both have the same configuration, but the iron compound has a higher nuclear charge. Thus it will react stronger with water ligands Mg compounds are a pale pink and absorb light in the green region Fe compounds are yellow/brown and absorb light in the blue range.

Charge Density of the Ligand The spectrum of the copper complex formed four water ligands is a very light blue colour. When mixed with NH3 ligand the solution colour is a darker blue. NH3 has a greater charge density than water and produces a larger split in thed-orbitals.

Spectrochemical Series. Arranges the ligands according to energy separation. Ligand I- Br- S2- Cl- H20 OH- NH3 CN- CO Max Frequency Longest Increasing Wavelength Shortest ΔE weakest ΔE Increasing Strongest