transition metals Flashcards
(63 cards)
what is a transition metal
a dblock element that forms at least one stable ion with partially filled d orbitals
what is a d block element
an element where it’s highest energy electrons are in a D subshell
why do chromium and copper only have 1 electron in 4s subshell
having a half-full, or entirely full, set of D orbitals is particularly stable
despite having a higher energy level than the 4s shell, the energy needed to promote an electron from 4s to 3d is less than the benefit of having a half full, or full, set of d orbitals
why can a transition metal form many different ions
there is a gradual increase in successive ionisation energies however they are very similar
how does a complex ion form
when a transition metal ion is surrounded by ions or other molecules that form coordinate bonds (ligands)
where do the electrons go in transition metal complex ions
into empty available D orbitals
what is a ligand
a molecule that can form coordinate bonds with a transition metal ion as it has a lone pair available to donate
why is a complex ion with 2 ligands linear
electron pairs in bonds are spaced out at maximum separation and minimum repulsion
why will a metal ion accept 6 water molecules as ligands but only 4 chloride ions as ligands
chloride ions have negative charge so they repel eachother
chloride ions are bigger than H2O so cannot fit 6 around metal ion at 90 degree angles
why are some complex ions with 4 ligands tetrahedral, and others square planar
square planar will occur if metal ion has lone pairs as there is increased repulsion on top/bottom
what is a monodentate ligand
a ligand that has 1 lone pair available for co-ordination to transition metal ions, as well as their shape
what is an example of a multidentate ligand
EDTA - 4- charge as has 4 letters
explain why complex ions are coloured
ligand causes D orbitals to split into higher and lower energy levels, different ligands cause different energy gaps
light passes through solution energy is absorbed, electrons promoted to high energy D orbitals
specific energy needed for energy gap is absorbed and all other light is transmitted in form of visible light
what can affect the colour of complex ions
transition metal ion (diff number of electrons)
charge of transition metal ion (diff number of electrons)
ligands (cause different splitting)
coordination number/shape
why is there a lack of colour in some complex ions
if d orbitals are full/empty electrons cannot move between the energy levels= no absorbance= no colour
coordination number meaning
number of coordinate bonds that exist in a complex ion
what shape do H2O OH- and NH3 ligands usually form
octahedral
what shape do Cl- ligands form
tetrahedral as they are larger ligands
what is an example of a square planar complex ion
cis/trans platin
why is cisplatin used in treatment of cancer and not transplatin
transplatin cannot form 2 coordinate bonds with adjacent nitrogenous bases (guanines) , it can only form 1 as chlorines are opposite eachother so DNA polymerase can easily break this bond and DNA can still replicate
how many coordinate bonds does EDTA make
6
what is haemoglobin
is an iron (II) complex containing a multidentate ligand
what is a ligand exchange reaction of haemoglobin
when an oxygen molecule is replaced by a carbon monoxide molecule
or when oxygen molecule replaces water molecule in lungs (breathe out water vapour)
2 examples of bidentate ligands
ethanedioate
ethane 1,2 diamine
