TRANSITION METALS - terms

complex

central metal ion surrounded by ligands

ligand

atom/ion/molecule which forms a coordinate bond by donating a pair of e^-

coordinate bond

shared pair of e^- in a covalent bond comes from only one/the same bonding atoms

coordination number

number of coordinate bonds formed to a central metal ion

monodentate

one coordinate bond formed per ligand bi

bidentate

2 atoms with lone pairs and can form 2 coordinate bonds per ligand

examples of monodentate ligands

H₂O / NH₃ / Cl^-

monodentate ligands features for H₂O / NH₃

• similar in size

• uncharged

• exchange occurs without change in coordination number

• BUT substitution may be incomplete

bidentate ligands example

NH₂CH₂CH₂NH₂ / C₂O₄^2- (ethanoate ion)

monodentate ligand features for Cl^-

• larger

• charged

• changes in coordination number may occur

is haem (iron (II) complex) multi or monodentate?

multidentate

how is oxygen transported in blood?

oxygen forms a coordinate bond with Fe (II) in haemoglobin which transports oxygen in blood

why is CO toxic?

CO forms a stronger coordinate bond with hemoglobin and prevents oxygen from attaching to haemoglobin, therefore less oxygen transported around body via blood

what is the chelating effect?

when substitution of a monodentate ligand with a bidentate/multidentate ligand forms a more stable complex

does the chelating effect cause a +ve or -ve entropy change, and why?

+ve because there’s more molecules of products > reactants

what shape and bond angle do small ligands (H₂O / NH₃) form?

• octahedral

• 90 degrees

what shape and bond angle do larger ligands (Cl^-) form?

• tetrahedral

• 109.5 degrees

what shape and bond angle does cisplatin form?

• square planar

  • 90 degrees

what shape and bond angle does Tollen’s reagent form?

• linear

• 180 degrees

how does colour of ions arise?

when some wavelengths of visible light are transmitted/reflected

what happens to the e^- when light is absorbed?

d e^- move from ground state to an excited state when light is absorbed