transition elements

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why is the structure of Cr [Ar]4s1 3d5 ?
because the repulsion between two paired electronsin the 4s orbital is more than the energy difference between the 4s and 3d subshells
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electrons from which subshell are removed first when creating a transition metal ion?
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what is a transition metal?
a metal which forms at least one stable ion with partially filled d-orbitals
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which d-block elements are not transition metals?
Zn, Sc as they only form +3 and +2 ions retrospectively. Zn as a full d subshell and Sc has an empty subshell.
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what is a complex ion?
an ion comprising of one or more ligands attached to a central metal cation by means of a dative covelant bond.
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what is a ligand?
a species which can use its lone pair of electrons to form a dative covelant bond with a transition metal.
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give examples of ligands.
H2O, NH3, Cl-, OH-
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which two features must a cation which forms a complex ion have?
a high charge density (to attract electrons from ligands) and empty orbitals of low energy.
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What shape is a 6-coordinate complex?
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which coordinate complex creates a tetrahedral shape?
a 4-coordinate complex with larger ligands such as Cl-
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what shape does Ag+ with two NH3 ligands form?
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what do all d-block exsist as in solution?
hexaaqua complexes
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what is the effect of ligands on a complex ion?
they satbalise the metal cation by increasing the size and hence reducing the polarizing power. (this makes the compounds more ionic)
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how are the properties of anions changed if they are behaving as ligands in a complex ion?
they are much less readily precipitated by cations
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how do the properties of molecules change if they are behaving as ligands?
they are less readily removed by heating
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what are ethandioate and 1,2-diaminoethane examples of?
bidentate ligands, which are ligand whichare capable of forming more than one dative covelant bond per ligand
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what example of a hexadentate is there?
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why are transition metal ions coloured?
d-electrons can absorb liht and get excited into higher energy d-orbitals. the resultant light is thus missing certain frequencies and is hence coloured.
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what two criteria must be satisfied for the ion to be coloured?
must be splitting of the d-orbitals (only happens in the presence of ligands). the d-orbitals must be patially filled.
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what technique can be used to determine the concentration of a solution containg a coloured ion?
ultraviolet and visible spectrophotometry
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what does the molecule haemoglobin consist of?
complex ion containing Fe2+, tetradentate ligand porphyrin, protein globin and a molecule of oxygen which forms the sixth coordinate bondwhat is
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what is [Ag(NH3)2]+ used for
to test for aldehydes and halides as it is the active ion in tollens reagent.
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what is a catalyst?
a substance which alter the rate of reaction but is chemically unchanged at the end. it lowers the activation energy by providing an alternative reaction pathway.
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what is the most common example of a reaction that needs a homogeneous catalyst?
a reaction between two anions as they repel each other, which decreases their chances of a collision.
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how do heterogeneous catalysts work?
allows the reactant molecules to bond to the surface of the metal, the reaction takes place at the surface and the products desorb.
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what is the difference between physical adsorbtion and chemisorbtion?
physical adsorbtion is where the molecules bond to the surface using intermolecular forces. chemisorbtion is where a covelant bond is formed.
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why is silver a bad catalyst?
it adsorbs molecules too weakly, and thereactant molecules do not spend enough time in contact with each other.
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what is a example of a catalyst which adsorbs too strongly?
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give examples of heterogeneous catalysts
Fe in the haber process, V2O5 in the contact process, Nickel in the hydrogenation of ethene
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how can a catalyst be poisioned by impurities?
they bond strongly to the catalyst surface and block it
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give examples of impurities which poision catalysts
sulphur which poisons iron in the haber process, and lead in catalytic converters
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which iron ion is a reducing agent?
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what colour and oxidation state is Mn in MnO4-?
Purple and +7
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how can the +7 oxidation state of purple Mn turn into the pale pink Mn2+
reduction by Fe2+ in acidic conditions
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what colour is vanadium with the oxidation state +5
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what is the oxidation state of the violet vanadium compound
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how does V with an oxidation state of +5 turn into +2?
by strong reducing agents such as zinc in acid solution
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electrons from which subshell are removed first when creating a transition metal ion?



Card 3


what is a transition metal?


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Card 4


which d-block elements are not transition metals?


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Card 5


what is a complex ion?


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