Chapter 24 - Transition Elements Flashcards
What are d-block elements?
3d sub-shell has the highest energy electron
What is the electron configuration for chromium?
1s2 2s2 2p6 3s2 3p6 3d5 4s1
3d5 gives additional stability
What is the electron configuration for copper?
1s2 2s2 2p6 3s2 3p6 3d10 4s1
3d10 gives additional stability
What are transition elements?
d-block elements that forms at least one ion with a partially filled d-orbital
Why are Sc and Zn not transition metals?
Sc will have empty d-orbital when it becomes Sc3+
Zn will have fully filled d-orbital when it becomes Zn2+
What are the three properties of transition metals?
- Different oxidative states
- Coloured compounds
- Act as catalysts
What is a complex ion?
Transition metal bonded to ligands by coordinate bonds
What are coordinate bonds?
Dative covalent bonds
What is coordination number?
Total number of coordinate bonds formed between a central metal ion and ligand (complex ion)
What is a ligand?
Molecule or ion that can donate a pair of electrons to a transition metal ion to form a coordinate bond
What is a dative covalent bond?
One of the bonded atoms provides both electrons for the shared pair
What is a monodentate ligand?
Donates one pair of electrons to the central metal ion
Forms one coordinate bond
What is a bidentate ligand?
Donates two pairs of electron to central metal ion
Forms two coordinate bonds
What shape do six coordinate complexes form?
Octahedral
What is the bond angle in an octahedral shaped complex?
90º
What shapes do four coordinate complexes form?
Tetrahedral
Square planar
What is the bond angle in a tetrahedral shaped complex?
109.5º
What is the bond angle in a square planar shaped complex?
90º
Which transition metals normally form square planar shaped complexes?
With d-electors in highest energy d-sub shell
- Pt (II)
- Pd (II)
- Au (III)
What shape of complexes does CIS-TRANS stereoisomerism occur in?
Square planar
Octahedral (monodentate & bidentate)
What shape of complexes does OPTICAL stereoisomerism occur in?
Octahedral (bidentate)
(only the cis-isomer!)
What colour and complex forms when copper (II) sulfate dissolves in water?
Pale blue [Cu(H2O)6]2+
What is formed in the precipitation reaction between Cu2+ and NH3?
Pale blue Cu(OH)2
SOLUBLE in excess ammonia
What is the colour and formula of the complex which forms when EXCESS ammonia is added drop-wise to copper (II) sulfate (aq)?
Dark blue [Cu(NH3)4(H2O)2]2+
Formula for EXCESS ammonia reacting with copper (II) sulfate (aq)?
[Cu(H2O)6]2+ + 4NH3 —> [Cu(NH3)4(H2O)2]2+ + 4H2O
What is the colour and formula of the complex which forms when EXCESS concentrated HCl is added to copper (II) sulfate (aq)?
Yellow [CuCl4]2-
Formula for EXCESS concentrated HCl reacting with copper (II) sulfate (aq)?
[Cu(H2O)6]2+ + 4Cl- —> [CuCl4]2- + 6H2O
Why does the coordination number and shape change in chloride ligand substitutition?
Chloride ligands larger so fewer can fit around central metal ion
What colour and complex forms when chromium (III) potassium sulfate dissolves in water?
Pale purple [Cr(H2O)6]3+
What is formed in the precipitation reaction between Cr3+ and NH3?
Grey green Cr(OH)3
SOLUBLE in excess ammonia
What is the colour and formula of the complex which forms when EXCESS ammonia is added drop-wise to chromium (III) potassium sulfate (aq)?
Purple [Cr(NH3)6]3+
Formula for EXCESS ammonia reacting with chromium (III) potassium sulfate (aq)?
[Cr(H2O)6]3+ + 6NH3 —> [Cr(NH3)6]3+ + 6H2O
What is formed in the precipitation reaction between Cu2+ and NaOH?
Pale blue precipitate Cu(OH)2
INSOLUBLE in excess NaOH
What is formed in the precipitation reaction between Fe2+ and NaOH?
Pale green precipitate Fe(OH)2
INSOLUBLE in excess NaOH
Turns brown at the surface when exposed to air as iron (II) gets oxidised to iron (III)
What is formed in the precipitation reaction between Fe3+ (pale yellow solution) and NaOH?
Orange brown precipitate Fe(OH)3
INSOLUBLE in excess NaOH
What is formed in the precipitation reaction between Mn2+ (pale pink solution) and NaOH?
Light brown precipitate Mn(OH)2
INSOLUBLE in excess NaOH
What is formed in the precipitation reaction between Cr3+ (pale purple solution) and NaOH?
Grey green precipitate Cr(OH)3
SOLUBLE in excess NaOH and forms a dark green solution containing [Cr(OH)6]3- complex
Solubilities of Fe2+, Fe3+, Mn2+ precipitates with excess ammonia?
Insoluble
What is the colour of Cu(s)?
Brown
What is the colour of I2(s)?
Brown
What is the colour of CuI precipitate?
White
