Transition metals Flashcards
what is a transition metal
element that has an incomplete d sub-shell in either its atoms or one of its common ions
Properties of transition metals
the incomplete d sub-shell is responsable for a number of general properties of the transition metal elements :
- variable oxidation states
- catalytic action
- coloured compounds
- formation of complexes
D- block element
are elements that have their outer most electrons in a d-orbital
Why is Zn not a transition metal?
Zn can only form a +2 ion. In this ion the Zn2+ has a complete d orbital and so does not meet the criteria of having an incomplete d orbital in one of its compounds.
Why is Sc not a transition metal?
Sc can only form a +3 ion. In this ion Sc3+ has an empty d orbital and so doesn’t meet the criteria of having an incomplete d orbial in one of its ions
What is the coordination number?
The of dative covalent bonds formed with the central metal ion
Example Q
Give the Electron configuration for Cr element
1s2 2s2 2p6 3s2 3p6 4s1 3d5
When doing electron configuration of ions, which electrons do you remove first in a + ion
The 4s orbital ions
Ligand substitution
What is a ligand?
- A ligand is an atom/ion/molecule that donates a pair of electrons to a central metal atom/ion.
- Needs at least one lone pair of electrons
- Otherwise it cannot form a dative covalent bond
Ligand substitution
What is a ligand with one lone pair called?
what examples ?
Monodentate (H2O, NH3, Cl-, OH-)
Ligand substitution
What is a ligand with two lone pairs called?
what examples ?
Bidentate e.g. 1,2-diaminoethane
Ligand substitution
Ligand with more than two lone pairs?
what examples ?
Multidentate e.g. EDTA4- (6 lone pairs) can form 6 dative bonds
Ligand substitution
What affects the size of the energy gap when ligands are bonded to metal ions?
Which central metal ion it is, its oxidation number, which ligands they are and the coordination number
Complexes
What are complex ions?
A complex ion is a metal ion surrounded by dative covalently bonded ligands
Complexes
What gives the distinctive shapes of complex ions?
The bonding electrons in the dative covalent bonds of a complex repel each other.
This means that they will try to get as far away as possible.
Causing complexes with different coordination numbers to have distinctive shapes.
complexes
Which ligand can only form 4 coordinate bonds?
Cl
what is the chelate effect ?
The replacement of monodentate ligands with bidentate and multidentate ligands in complex ions
It is an energetically favourable reaction, meaning that ΔGꝋ is negative
The driving force behind the reaction is entropy
complexes
Haemoglobin contains ___ ions
Fe2+
complexes
Haemoglobin forms an ____ shape
octahedral
Complexes
Haem
A square planar ligand attached to a ferrous group
Complexes
Globin
A complex protein molecule attached to a ferrous group from below
Complexes
Which complex ion can only form 2 coordinate bonds?
Ag
Example Q
why is CO toxic ?
Carbon monoxide is toxic because it is a better ligand than oxygen and binds strongly and irreversibly to the iron(II) preventing oxygen from being carried to the cells
complexes
what is Ethanedioate ?
4
- A bidentate ligand that has two negative charges
- C2O2−4
- colourless
- naturally occuring in some food