5.3.1 Transition Elements Flashcards
transition element
d block elements that form at least one ion with a partially filled d-orbital
in terms of electron configuration, what are the 2 exceptions?
chromium - half filled d sub-shell
copper - fully filled d sub-shell
for additional stability
why aren’t zinc and scandium transition elements?
Sc forms Sc³⁺, and has an empty d-orbital
Zn forms Zn²⁺, and has a full d-orbital
what are the 3 characteristic properties of transition elements?
- form compounds in which the transition element has different oxidation states
- form coloured ions
- the elements and their compounds can act as catalysts
ligand
molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate bond
example of complex ion with six-fold coordination with an octahedral shape
[Cu(H₂O)₆]²⁺
[Fe(H₂O)₆]³⁺
example of complex ion with four-fold coordination with a tetrahedral shape
[CuCl₄]²⁻
[CoCl₄]²⁻
example of complex ion with four-fold coordination with a planar shape
[Pt(NH₃)₂Cl₂]
coordination number
no. coordinate bonds attached to the central metal ion
what is a monodentate ligand?
a ligand that is able to donate one pair of electrons to a central metal ion
eg. H₂O, NH₃, Cl⁻
what is a bidentate ligand?
a ligand that is able to donate two pairs of electrons to a central metal ion
eg. NH₂CH₂CH₂NH₂, ⁻OOCCOO⁻
what’s the bond angle for an octahedral complex ion with 6 coordinate bonds?
90°
what’s the bond angle for an tetrahedral complex ion with 4 coordinate bonds?
109.5°
what’s the bond angle for an square planar complex ion with 4 coordinate bonds?
90°
what are the two types of stereoisomerism that complex ions display?
- cis-trans
- optical
what type of complex ions does cis-trans isomerism occur in?
square planar eg. [Pt(NH₃)₂Cl₂]
octahedral eg. [Co(NH₃)₄Cl₂]⁺
what type of complex ions does optical isomerism occur in?
octahedral complexes containing two or more bidentate ligands eg. [Ni(NH₂CH₂CH₂NH₂)₃]²⁺
what is cis-platin and what are its uses?
[Pt(NH₃)₂Cl₂] (square planar)
anti-cancer drug as it attacks tumours
forms a platinum complex inside a cell that binds to DNA and prevents cell division. Causes apoptosis.
ligand substitution reaction of [Cu(H₂O)₆]²⁺ with excess ammonia and colour change
[Cu(H₂O)₆]²⁺ + 4NH₃ → [Cu(NH₃)₄(H₂O)₂]²⁺ + 4H₂O
pale blue solution → dark blue solution
ligand substitution reaction of [Cu(H₂O)₆]²⁺ with excess concentrated HCl and colour change
[Cu(H₂O)₆]²⁺ + 4Cl⁻ ⇌ [CuCl₄]²⁻ + 6H₂O
pale blue solution → yellow solution
octahedral changes to tetrahedral (coordination no. changes as Cl⁻ are larger than H₂O ligands and fewer can fit around the Cu²⁺ ion
what is formed if [Cu(H₂O)₆]²⁺ reacts with a small amount of ammonia?
Cu(OH)₂
blue precipitate
this dissolves in excess ammonia to form a dark blue solution of [Cu(NH₃)₄(H₂O)₂]²⁺
ligand substitution reaction of [Cr(H₂O)₆]³⁺ with excess ammonia and colour change
[Cr(H₂O)₆]³⁺ + 6NH₃ → [Cr(NH₃)₆]³⁺ + 6H₂O
violet solution → purple solution
what is formed if [Cr(H₂O)₆]³⁺ reacts with a small amount of ammonia?
Cr(OH)₃
grey-green precipitate
this dissolves in excess ammonia to form a purple solution of [Cr(NH₃)₆]³⁺
what’s the biochemical importance of Fe²⁺ in Hb?
Fe²⁺ binds to O₂, forming oxyhaemoglobin and enabling oxygen to be transported in blood
what happens when you breath in CO?
ligand substitution reaction happens where O₂ is replaced by CO in the coordinate bond, forming carboxyhaemoglobin. This is irreversible as CO binds more strongly than O₂
Cu²⁺ with NaOH(aq) observations and ionic eq.
pale blue solution → blue precipitate of Cu(OH)₂
Cu²⁺(aq) + 2OH⁻(aq) → Cu(OH)₂(s)
precip is insoluble in excess NaOH
Fe²⁺ with NaOH(aq) observations and ionic eq.
pale green solution → green precipitate of Fe(OH)₂
Fe²⁺(aq) + 2OH⁻(aq) → Fe(OH)₂(s)
precip is insoluble in excess NaOH
precip is oxidised in air to Fe(OH)₃ (orange-brown precip)
Fe³⁺ with NaOH and NH₃(aq) observations and ionic eq.
pale yellow solution → orange-brown precipitate of Fe(OH)₃
Fe³⁺(aq) + 3OH⁻(aq) → Fe(OH)₃(s)
precip is insoluble in excess NaOH & and NH₃
Mn²⁺ with NaOH and NH₃(aq) observations and ionic eq.
pale pink solution → light brown precipitate of Mn(OH)₂
Mn²⁺(aq) + 2OH⁻(aq) → Mn(OH)₂(s)
precip is insoluble in excess NaOH & and NH₃
precip darkens in air
Cr³⁺ with NaOH and NH₃(aq) observations and ionic eq.
violet solution → grey-green precipitate of Cr(OH)₃
Cr³⁺(aq) + 3OH⁻(aq) → Cr(OH)₃(s)
precip is soluble in excess NaOH, forming dark green solution of [Cr(OH)₆]³⁻
Cr(OH)₃(s) + 3OH⁻(aq) → [Cr(OH)₆]³⁻(aq)
precip is soluble in excess NH₃, forming [Cr(NH₃)₆]³⁺ which is purple
colour of [Cu(H₂O)₆]²⁺
pale blue solution
colour of [Cu(NH₃)₄(H₂O)₂]²⁺
dark blue solution
colour of Cu(OH)₂
blue precipitate
colour of [CuCl₄]²⁻
yellow solution
colour of [Cr(H₂O)₆]³⁺
violet solution
colour of [Cr(NH₃)₆]³⁺
purple solution
colour of Cr(OH)₃
grey-green precipitate
colour of Fe(OH)₂
green precipitate
colour of [Fe(H₂O)₆]²⁺
pale green solution
colour of [Fe(H₂O)₆]³⁺
pale yellow solution
colour of Fe(OH)₃
orange-brown precipitate
colour of [Mn(H₂O)₆]²⁺
pale pink solution
colour of Mn(OH)₂
light brown precipitate
