Chapter 24 - Transition elements Flashcards
Which two elements don’t follow the typical electron figuration?
Chromium and copper
Why isn’t scandium classified as a transition metal?
A transition metal forms at least one ion with a partially filled d-orbital
Scandium forms Sc3+ by losing two 4S electrons and one 3D
Why isn’t zinc classified as a transition metal?
Zn2+ has a full d-orbital
Characteristics of transition metals
The element can have variable oxidation states
They form coloured compounds
Can act as catalysts
Which transition metal has the largest amount of oxidation states?
Manganese
What colour is iron (II)?
Pale green
What colour is iron (III)?
Yellow
What colour is Cr (III)?
Green
What colour is Cr (VI)?
Dark yellow
What catalyst is used in the Haber process?
Iron
What catalyst is used in the Contact process?
Vanadium oxide
What catalyst is used to hydrogenate vegetable fats?
Nickel
What catalyst is used to decompose hydrogen peroxide?
Manganese oxide
What are heterogenous catalysts?
The catalyst is in a different state to the reactants
What are homogenous catalysts?
The catalyst is in the same state as the reactants
When will a complex ion form?
When one or more molecules bond to a central atom
What is a ligand?
A molecule that donates a pair of atoms to a central molecule to form a dative covalent bond
What is the coordinate number?
The number of coordinate bonds attached to that atom
What is a monodentate ligand?
It is able to donate one pair of electrons to the central atom
What are bidentate ligands?
Able to donate two pairs of electrons to a central atom
What is the shape of a complex ion with a coordination number of 6?
Octahedral
When will a complex ion form a tetrahedral shape?
When it has a coordination number of 4
When will a complex ion form a square planar shape?
When it has a coordination number of 4 and the ion is of a transition metal
When will a complex ion exist as cis-trans isomers?
When octahedral complexes consist of four of one type of ligand and two of another type
When will optical isomerism occur?
Octahedral complexes containing 2+ bidentate ligands
What is a ligand substitution reaction?
One ligand or complex ion is replaced by another
What colour is the solution formed when copper (II) sulphate is dissolved in water?
Pale blue
What happens when excess ammonia is added to [Cu(H2O)6]?
Four water ligands are replaced by four ammonia ligands
In the first stage of the reaction, pale blue Cu(OH)2 is formed
Cu(OH)2 dissolves to form a darker blue solution
What happens when excess HCl is added to [Cu(H2O)6]?
Six water ligands are replaced by 4 chloride ligands
Pale blue solution changes yellow
What complex ion is formed when chromium (II) potassium sulphate is dissolved in water?
[Cr(H2O)6]3+
What colour is [Cr(H2O)6]?
Pale purple
Which complex ion is formed when chromium (II) sulfate is dissolved in water?
[Cr(H2O)5 SO4]+
Describe the reaction that occurs when ammonia is added to [Cr(H2O)6] 3+
Initially, grey-green Cr(OH)3 is formed
This dissolves in the ammonia to form [Cr(NH3)6]3+
What happens when carbon monoxide is breathed in?
A ligand substitution reaction takes place - oxygen in oxyhemoglobin is replaced by carbon monoxide
What is a precipitation reaction?
Two aqueous solutions form an insoluble ionic solid
What is produced when Cu2+ reacts with NaOH?
Blue copper hydroxide is produced, which is insoluble in sodium hydroxide
What is produced when Fe2+ reacts with NaOH?
Green iron (II) is formed, which is insoluble in NaOH Upon standing, the iron is oxidised to form iron (III)
What is produced when Fe3+ reacts with NaOH?
Orange brown iron (III) hydroxide is formed
Insoluble in NaOH
What is produced when Mn2+ reacts with NaOH?
Light brown manganese hydroxide is formed, which is insoluble in NaOH
What happens when Cr3+ reacts with NaOH?
Grey-green chromium hydroxide is formed, which is soluble in NaOH and forms a green solution
What happens to Fe2+ when it is titrated?
Oxidised to Fe3+
What happens to MnO4- when it is titrated?
Reduced to Mn2+
What colour are dichromate ions?
Orange
What colour are chromium ions?
Green
How are dichromate ions changed into chromium ions?
Addition of zinc - Cr2O72- is reduced
Equation for the oxidation of Cr3+ to CrO42-
3H2O2 + 2Cr3+ + 10OH- -> 2CrO42- + 8H2O
What happens when I- reacts with Cu2+?
I- is oxidised to I2
Cu2+ is reduced to Cu+
Equation for I- reacting with Cu2+
2Cu2+ +4I- ->2CuI + I2
How to test for the ammonium ion?
NaOH is heated with the solution being analysed
If ammonia is present, litmus paper will turn red
What is a ligand substitution reaction?
One ligand in a complex ion will be replaced by another
What colour is the solution formed when copper (II) sulfate is dissolved in water?
Pale blue
What happens when excess ammonia is added to a solution containing [Cu(H2O)6] and why?
The pale blue colour changes to a dark blue one
4 ammonia molecules have replaced 4 of the water molecules in the complex ion
