Transition Metals
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Where are the transition metal elements found in the periodic table?
The central d block of the periodic table
Where are the transition metal elements found in the periodic table?
The central d block of the periodic table
What are the common properties of period 4 elements?
• they form complex ions • their ions are coloured • they show catalytic activity • their oxidation states are variable
What is a transition metal defined as?
An element that has an incomplete d subshell either in the element or in one of its ions
What are the properties of transition elements directly related to?
The electronic structures of their atoms
The 4s subshell usually fills before the 3d subshell. What can chromium and copper do that leads to a more stabilised d subshell?
They can promote a 4s electron to the d subshell and this gives rise to a half-filled and fully filled d shell which are stabilised.
Why do transition metal atoms lose 4s electrons before 3d electrons?
Because if electrons occupy the 3d subshell the 4s subshell increases to a higher energy level
Why are zinc and scandium not considered transition metals?
• the normal ion formed in scandium compounds is Sc(III). This has no electrons in the d orbital - its electron configuration is [Ar] 3d04s0 so it isn’t considered a transition metal • zinc forms Zn(II) compounds with the configuration [Ar]3d104s0. It is not considered a transition metal because the d subshell is complete
What do transition metals in water solutions do?
Form coordination complexes with water
What are complexes with water ligands called and how may they be represented?
They’re called metal-aqua ions and may be representer as Co2+(aq) ect..
In a complex what is the number of bonds formed between the metal ion and lone pair from the ligands called?
The coordination number
What are ligands?
Molecules or ions which share an electron pair with a metal ion to form a coordination complex
What is the reaction of the replacement of one or more ligands called?
Ligand substitution
What are divalent meral-aqua ions?
They have a 2+ charge
What is the trend in the reactivity of divalent metal aqua ions in the fourth period?
It increases from Mn2+ to Cu2+
What happens to the coordination mumber in ligand substitution between water and ammonia?
It doesn’t change as they are neutral molecules of similar size
What is complete and incomplete ligand substitution?
• complete substitution occurs when all ligands are replaced * incomplete substitution occurs when only some of the ligands are replaced
What is the overall reaction of Cu2+(aq) with NH3 made up of?
Four seperate equilibrium reactions. And each of these ligand substitution reactions has it’s own equilibrium constant
What can the equations for all the ligand substitution reactions be simplified to give?
A dissociation constant of the complex Kd
What is the formation constant, Kf?
The reciprocal of the complex dissociation constant Kf=1/Kd
Why does the ligand substitution of water with Cl- from H involve a change in coordination number from 6 to 4? [Cu(H2O)6]2+ + 4Cl- [CuCl4]2- + 6H2O
Becayse halide ions are negatively charged ligands that are much larger than water or ammonia and metal ions of the fourth period are too small to coordinate six halide ions
What is the difference between bidentate ligands and monodentate ligands?
Bidentate ligands have two electron pairs each (are said to have two teeth) whereas monodentate ligands have one electron pair (one tooth)
What are multidentate ligands and what do they form with transition metals?
They have more than two electron pairs. They can form very stable complexes with transition metal ions
What are all chemical reactions governed by?
The second law of thermodynamics?