Unit 2: Section 4 - Transition Metals Flashcards
Definition : transitional metal
A metal that can form one or more stable ions with a partially filled d sub-level.
Which metals in the d-block are not transition metals?
scandium only forms one ion Sc ^3+ with an empty d sub-level.
zinc only forms one ion Zn^2+ with a full d sub-level
Transitional metals: physical properties (3)
1) high density
2) high melting point and high boiling point
3) ionic radii are more or less the same
transitional metals: chemical properties (4)
1) form complex ions
2) form colored ions
3) good catalysts
4) exist in variable oxidation states
Color: MnO4 -
purple
Color: Cr2O7 2-
orange
Color: VO2 +
yellow
Color: VO 2+
blue
Color: V 3+
green
Color: Cr 3+
violet / green
Color: Fe 3+
purple / yellow
Color: V 2+
violet
Color: Mn 2+
pale pink
Color: Fe 2+
pale green
Color: Co 2+
pink
Color: Ni 2+
green
Color: Cu 2+
blue
Definition: a complex
A central metal atom or ion surrounded by coordinately bonded ligands.
Definition: a co-ordinate bond
a covalent bond in which both electrons in the shared pair come from the same atom.
Definition: ligand
an atom, ion or molecule that donates a pair of electrons to a central transitional metal ion to form a co-ordinate bond.
Definition: co-ordination number
the number of co-ordinate bonds that are formed with the central metal ion.
What shape will a complex be with six co-ordinate bonds?
An octahedral shape with 90 degree angles.
What shape will a complex be with 4 co-ordinate bonds?
A tetrahedral shape with 109.5 degree angles or a square planar shape with 90 degree angles.
What shape will a complex be with 2 co-ordinate bonds?
A linear shape with 180 degree bond angle.
Formula for the oxidation state of the metal ion
total oxidation state - the sum of the oxidation states of the ligands
Definition: multidentate
ligands that can form more than one co-ordinate bond
Definition: monodentate
ligands can only form one co-ordinate bond
What happens to haemoglobin in the lungs?
The oxygen concentration is high, an oxygen molecule substitutes the water ligand and bonds coordinately to the Fe (II) ion to form oxyhaemoglobin, which is carried around the body in the blood,
What happens to haemoglobin in muscle tissue?
The oxygen molecule is exchanged for a water molecule and the heamoglobin returns to the lungs again.
Components of haemoglobin
Fe 2+, H2O , four N , globin protein (another N)
Definition: optical isomerism
where an ion can exist in two forms that are non-superimposable mirror images.
cis- isomerism
If two odd ligands are next to each other
trans- isomerism
if the two odd ligands are opposite each other
How do ligands split the 3d Sub-level into two energy levels?
3d orbitals of transition element ions all have the same energy. When ligands bond to the ions some of the orbitals gain energy which splits the 3d orbitals to two different energy levels.
How do electrons jump to higher orbitals?
Electrons tend to occupy lower orbitals and to jump up to the higher orbitals they need energy equal to the energy gap. They get this from visible light.
How is energy absorbed (AE), Planck’s constant (h), frequency of light absorbed (v)
AE = hv
How are the colors of compounds formed?
When visible light hits a transition metal ion, some frequencies are absorbed when electrons jump up to the higher orbitals. The frequencies absorbed depend on the size of the energy gap. The rest of the frequencies are transmitted or reflected. These transmitted or reflected frequencies combine to make the complement of the color of the absorbed frequencies.
Factors which can affect the size of the energy gap (3)
1) changes in oxidation
2) changes in co-ordination number
3) changes in ligand
How can spectroscopy be used to find concentrations of transition metal ions?
White light is shone through a filter which is chosen to only let through the color of light that is absorbed by the sample. The light passes through the sample to a colorimeter, which calculates how much light was absorbed by the sample. The more concentrated a colored solution is, the more light it will absorb.
Aluminum hydroxide precipitate + sodium hydroxide excess
will dissolve because it’s amphoteric
copper hydroxide precipitate + ammonia excess
dissolves because it undergoes a ligand exchange reaction with excess ammonia
sodium carbonate + Fe 3+/ Fe 2+
Fe 3+ will give off a gas whilst Fe 2+ will not
