unit 1a: transition metals Flashcards
transition metals
metals with an incomplete d-subshell in at least one of their ions
variable valency
transition metals can form ions with different charges by losing different numbers of electrons
scandium and zinc
these are not transition metals as there is not an incomplete d-subshell in the ions they form
properties
form coloured ions, form complexes, variable oxidation states, show catalytic activity
oxidation state
an element is said to be in a particular oxidation state when it has a specific oxidation number, related to the number of electrons the species has lost or gained
oxidation number in a free element
0 e.g. Mg=0 and Cl2=0
for monatomic ions, the oxidation number is
equal to the charge, e.g. Cl^-1=-1 and Al^3+=+3
oxidation number for oxygen
-2
oxidation number for hydrogen
+1
group 1 metals and group 2 metals
+1 and +2
oxidation number in compounds
fluorine, the CN^-1 ion, and all of group 7 is always equal to -1
in molecule the sum of all oxidation numbers is
equal to 0, e.g. H20=0
in a polyatomic ion, the sum of the oxidation numbers is
equal to the charge of the ion, e.g. SO4^2-=-2
oxidation involves
increase in oxidation number
reduction involves
decrease in oxidation number
metals high in oxidation states tend to be good
oxidising agents
what two elements in the box are not transition metals
scandium and zinc
redox acronym
OILRIG
ligand definition
electron donors, may be negative ions or molecules with non-bonding pairs of electrons
a complex consists of
a central metal ion surrounded by ligands
dative bond
when both electrons of the shared pair come from the same atom
ligands have at least
one lone pair of electrons
monodentate
when a ligand uses just one atom to bind to the central metal
bidentate
when a ligand uses two atoms to bind to the central metal
example of a hexadentate ligand
ethylenediaminetetraacetate- EDTA
monodentate ligands- negative ions
fluoride F- , chloride Cl- , cyanide CN-
monodentate ligands- neutral molecules
water H2O , ammonia NH3
bidentate ligand- negative ion
oxalate C2O4^2-
coordination number
the total number of bonds from the ligands to the central transition metal atom/ion