A level OCR Chemistry module 5.3

CHEMISTRY
MODULE 5 – PHYSICAL CHEM & TRANSITION ELEMENTS
5.3 – TRANSITION ELEMENTS

5.3.1 Transition elements

 Define the tem transition element
o D-block elements forming one or more stable ions with partially
(incomplete) d-subshells ie Ti-Cu

 Give the electron configuration of a chromium atom
o 1s22s22p63s23p63d54s1

 Give the electron configuration of a copper atom
o 1s22s22p63s23p63d104s1

 Understand why Sc and Zn are not transition elements
o Sc only forms Sc3+, which has an empty d-subshell
o Zn only forms Zn2+ which has a full d-subshell

 Describe the characteristic properties of transition elements
o They can form variable oxidation states – the energy levels of the 4s
and 3d subshells are close to each other. Different numbers of
electrons can be gained or lost using similar amounts of energy
o They can form coloured ions – due to the partially filled d-subshells
o They are good catalysts – because they can transfer electrons within
their d orbitals speeding up reactions
 Cu2+ is used for the reaction of Zn with acids
 MnO2 is used for the decomposition of H2O2

 Define the term complex ion
o Is a metal ion surrounded by co-ordinately bonded ligands

 Define the term ligand
o An atom, ion or molecule which can donate a lone electron pair to form
a co-ordinate bond to a metal ion or metal

 Define the term co-ordination number
o Is the number of co-ordinate bonds formed to a central metal ion.

 Define the term unidentate ligand
o These are ligands which can form one coordinate bond per ligand (eg
H2O, NH3, Cl-, CN-)

 Define the term bidentate ligand
o These have two atoms with lone pairs and can form two coordinate
bonds per ligand (eg NH2CH2CH2NH2 [en] or ethanedioate ion C2O42-)