Transition Metals Flashcards
Where are the transition metals on the periodic table?
They are directly under and include the row between titanium to copper.
Physical properties of elements from titanium to copper.
Good conductors of heat and electricity. Hard, strong, shiny and have high melting and boiling points.
Which orbital are the first electrons gained or lost from for the first row of transition metals?
4s
Define a transition element
An element that forms at least one stable ion with a part full d-shell of electrons.
Chemical properties of transition metals
They have variable oxidation states. They form coloured ions. They or their compounds can show catalytic activity. They form complex ions.
What is a complex ion?
A transition metal surrounded by ions or other molecules (collectively ligands) which are bonded to it by co-ordinate bonds.
What is a ligand?
An atom, ion or molecule that forms a co-ordinate bond with a transition metal ion using a lone pair of electrons.
What is the co-ordination number?
The number of co-ordinate bonds to ligands that surround the d-block metal ion.
Shapes and examples for co-ordination numbers 2,4,6
2: linear. Example Ag+ complexes
4: tetrahedral (more common). Example large ligands like Cl-
4: square planar (less common). Example Pt2+ or Ni2+ complexes
6: octahedral. Most common out of all transition metals.
What is a Lewis acid?
An electron pair acceptor.
What is a Lewis base?
An electron pair donor.
What are aqua ions and how do they form?
If you dissolve the salt of a transition metal in water, the positively charged metal ion becomes surrounded by water molecules acting as ligands. Normally there are 6 water molecules in an octahedral arrangement. The resulting species are called aqua ions.
What is a multidentate ligand?
A ligand that has more than one atom with a lone pair of electrons which can bond to a transition metal ion.
Which ligand is often abbreviated to en?
Ethane-1,2-diamine
How many do-ordinate bonds can EDTA have and what is its charge?
6 bonds
4-
What are chelates?
Complex ions with polydentate ligands
What is the chelate effect?
Where chelate complexes with polydentate ligands are favoured over complexes with monodentate ligands. There is an increase in entropy and the change in enthalpy is negligible as the same number of the same type of similar bonds are being broken and formed.
What is chelation?
The process by which a multidentate ligand replaces a monodentate ligand in forming co-ordinate bonds to a transition metal ion
How to draw complex ions
Put metal in middle. Draw 3D bond shape. Add ligands. Draw square brackets around whole molecule. Put charge in top right, X+.
Describe cis-trans (geometrical) isomerism in complexes
A special type of E-Z isomerism. Occurs in octahedral or square planar complexes when there are two types of ligand. The ligands of the same type could be next to each other (cis) or on opposite sides of the central metal ion (trans).
Describe optical isomerism in complexes
Happens when there are 2 or more bidentate ligands is an octahedral complex. The two optical isomers are mirror images of each other and rotating either one cannot make the ligands all go in the same positions as the other.
Why are transition metal complexes coloured?
The transition metals have part filled d orbitals. It’s therefore possible for electrons to move from one d orbital to another. In a compound, the presence of other atoms nearby makes the d orbitals have slightly different energies. Electrons move from one d orbital (in ground state) to another of a higher energy level (excited state) if they absorb energy equal to the difference in energy between levels. This energy is often in the visible part of the EM spectrum. This colour is therefore missing from the spectrum and you see a combination of the colours not absorbed.
What affects the colour of transition metal complexes?
The energy gap between d orbitals. This is affected by the oxidation state of the metal, the type of ligands and the shape of the complex ion.
Colour and formula of Vanadium in oxidation states +5 to +2
\+5 is VO2 +, yellow \+4 is VO 2+, blue \+3 is V 3+, green \+2 is V 2+ violet All aqueous. You Better Get Vanadium