Unit 2: Section 4 - Transition metals CDS * Flashcards
transition metals - the basics complex ions more on complex ions formation of coloured ions substitution reactions variable oxidation states titrations with transition metals catalysts metal-aqua ions more on metal-aqua ions
what is a transition metal?
A transition metal is a metal that can form one or more stable ions with a partially filled d sub-shell
where can transition metals be found in the periodic table?
in the d - block
which elements in the period 4 d-block are transition metals?
all of them except scandium and zinc
remember chromium and copper only have 1 electron in their 4s orbital and all the rest have 2
what causes the special chemical properties of transition metals?
the incomplete d sub-shell
why isn’t scandium a transition metal?
scandium only forms 1 ion, Sc 3+, which has an empty d sub-shell
electron configuration of Sc 3+ = [Ar]
why isn’t zinc a transition metal?
it only forms 1 ion, Zn 2+, which has a full d sub-shell
electron configuration of Zn 2+ = [Ar] 3d^10
what happens when transition metals form ions?
the s electron are removed first, then the d electrons to form positive ions
what physical properties do transition metals have?
high density
high melting and boiling points
ionic radii are very similar
what chemical properties do transition metals have?
can form complex ions
form coloured ions
good catalysts
exist in variable oxidation states
what colours can vanadium ions be?
VO2 = yellow
VO 2+ = blue
V 3+ = green
V 2+= violet
what colour can chromium ions be?
Cr2O7 2- = orange
Cr 3+ = green (violet with water ligands)
what colour can manganese ions be?
MnO4 - = purple
Mn 2+ = pale pink
what colour can iron ions be?
Fe 3+ = yellow (purple with water ligands)
Fe 2+ = pale green
what colour can cobalt, nickel and copper ions be?
Co 2+ = pink
Ni 2+ = green
Cu 2+ = blue
why do transition metals have variable oxidation states?
the energy levels of the 4s and 3d sub - levels are very close to one another. so different numbers of electrons can be gained or lost using fairly similar amounts of energy
what is a complex?
a complex is a central atom or ion surrounded by coordinately bonded ligands
what is a coordinate (dative covalent) bond?
a covalent bond in which both electrons in the shared pair come from the same atom.
in a complex they come from ligands
what is a ligand?
an atom, ion or molecule that donates a lone pair of electrons to a central transition metal ion to form a co-ordinate bond
what is the coordination number?
the number of coordinate bonds that are formed with the central metal ion
when is the co-ordination number 6?`
when the ligands are small: H2O, NH3
shape: octahedral
bond angles: 90*
the O or the N donates the electrons
when is the co-ordination number 4?
if the ligands are larger: Cl-
shape: tetrahedral
bond angle: 109.5*
when is a complex square planar?
platinum or nickel centre
e.g. platinum centre with 2 NH3 ligands and 2 Cl - ligands
bond angle: 90*
when is the co-ordination number 2?
when the metal ion centre is silver
shape: linear
bond angle: 180*
what is the overall charge of a complex ion?
a.k.a. total oxidation state
the charge outside the square brackets of the complex