5.7 Transition Elements Flashcards
What are d-block elements ?
D-block elements are located between group 2 and group 13 of the periodic table. Across the period, the 3d sub-shell has the highest energy and electrons are added to 3d orbitals.
What does electronic configuration show ?
It shows the arrangement of electrons in shells and sub-sells. Electrons occupy orbits in order of increasing energy.
What are the exceptions of electronic configuration of transition elements ?
Chromium and copper do not follow the expected principle for placing electrons singly in orbitals before pairing. Half filled d5 sub-shell and fully filled d10 sub-shell give additional stability.
What are rules for 4s and 3d sub shells when forming an atom or ion ?
When forming an atom, the 4s orbital fills before the 3d sub shell.
When forming an ion, the 4s orbital empties before the 3d orbitals.
What are transition elements ?
They are defined as d-block elements that form at least one known ion with a partially filled d-orbital.
Why is scandium not a transition metal ?
It is a d-block element but only form 3+ ion by loss of 2 4s electrons and 1 3d electron so has empty 3d sub-shell.
Why is zinc not a transition metal ?
Zinc only forms the 2+ ions by the loss of 2 of its 4s electrons so has a full 3d sub-shell.
What are the properties of transition metals ?
They form compounds in which the transition element has different oxidation states. They form coloured compounds and their elements and their compounds can act as catalysts.
Why are transition metals described as having variable oxidation states ?
Transition elements form compounds with more than one oxidation state and the number of oxidation states increases across the elements and then decreases after manganese. All transition elements form compounds with an oxidation number of +2.
What coloured is potassium dichromate represented as ?
Bright orange.
What coloured is cobalt chloride represented as ?
Pink/ purple.
What coloured is nickel sulphate represented as ?
Green.
What coloured is hydrated copper sulphate represented as ?
Blue.
What is the colour of transition elements linked to ?
Linked to partially filled d-orbitals of the transition metal ion. The colour of the solution can vary with different oxidation states.
How are transition metals used as catalysts in the Haber process ?
The reaction between nitrogen and hydrogen is catalysed by a finely divided iron catalyst. This is an example of heterogeneous catalysts.
How are transition metals used as catalysts in the reaction between iodide ions and peroxodisulphate ions ?
This is catalysed by Fe2+ ions, with reactants and catalysts all in aqueous solutions.
What are complex ions ?
Complex ions are formed when one or more molecules or negatively charged ions bond to a central metal ion.
What are ligands ?
A ligand is a molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate bond or dative covalent bond.
What is the coordination number ?
The coordination number indicates the number of coordinate bonds attached to the central metal ion.
How do you represent complex ions ?
Complex ions are enclosed inside square brackets with the overall charge of the ion presented.
What are mono dentate ligands ?
This is a ligand that is able to donate one pair of electrons to a central metal ions. Eg. H2O, NH3, CL-, CN-, OH-.
What are bidentate ligands ?
This is a ligand that can donate 2 lone pairs of electrons to the central metal ion. Eg. en, ethanedioate ion.
What shape is a complex ion with a coordination number of 6 ?
This is an octahedral shape with bond angles of 90 degrees.
What shape is a complex ion with a coordination number of 4 ?
Can either be tetrahedral Wirth 109.5 bond angles or can be square planar with bond angles of 90 degrees.
What are stereoisomers ?
They have the same structural formula but a different arrangement of atoms in space.
In what complex ions does cis-trans isomerism occur ?
Can occur in some square planar and octahedral complex ions.
What are cis isomers in complex ions ?
Two identical groups are adjacent to each other with bonds between the same ligands being 90 degrees.
What are trans isomers in complex ions ?
Two identical group are opposite each other with bonds between the same ligands being 180 degrees.
What is optical isomerism ?
Optical isomerism only occurs in octahedral complexes containing 2 or more bidentate ligands. They are non-superimposable mirror images of each other.
What is a ligand substitution reaction ?
This is when one or more in a complex ion is replaced by another ligand.
What observation when ammonia is added to Cu 2+?
Blue solution form blue ppts then in excess turns a dark blue solution.
What is the complex ion when Cu2+ solution reacts with ammonia ?
[Cu(NH3)4(H2O)2] 2+
What observation when concentrated HCl is added to Cu2+ ?
Green solution forms a yellow solution.
What is the complex ion when Cu2+ reacts with HCl ?
[CuCl4] 2-
What observation when ammonia is added to Cr 3+ ?
Pale purple solutions forms a grey/green ppt and then forms a green solution when ammonia is added in excess.
What is the complex ion when ammonia is added to Cr3+ ?
[Cr(NH3)6] 3+
What observation when concentrated HCl is added to Cr3+ ?
Violet solution turns to blue solution.
What is the complex ion when HCl reacts with Cr 3+ ?
[CrCl6] 3-
What is a precipitation reaction ?
They occur when 2 aqueous solutions containing ions react together to form an insoluble ionic solid.
What is the observation of Cu 2+ with NaOH ?
Blue solutions forms blue ppt of copper hydroxide. The ppt is insoluble in excess of sodium hydroxide.
What is the observation of Fe 2+ with NaOH ?
Pale green solution reacts to form a green ppt of iron hydroxide. Ppts is insoluble in excess but turns brown at standing.
What is the observation of Fe 3+ with NaOH ?
Pale yellow solution reacts to form an orange/brown ppt of precipitate of iron hydroxide. Ppt is insoluble in excess sodium hydroxide.
What is the observation of Mn 2+ with NaOH ?
Pale pink solution reacts to form a light brown ppt of manganese hydroxide, which darkens on standing in air. Ppt is insoluble in excess sodium hydroxide.
