Transition element ch28 Flashcards
Transition element
A d-block element which form one or more stable ions with incomplete d orbitals
Physical properties of transition elements
- High melting and boiling point
- High electrical conductivity
- High density
Why does transition elements have high melting and boiling point
Greater number of delocalised electrons, giving stronger metallic bonding
Why does transition elements have high electrical conductivity
Greater number of delocalised electrons
Why does transition elements have high density
Larger Ar value but smaller atomic radius
Transition elements chemical properties
- Variable oxidation states
- Homogenous catalyst
- Heterogenous catalyst
- Form complex ions
Why do transition elements have variable oxidation states
Close similarity of energy level between 3d and 4s orbitals
Why can transition elements be homogenous catalyst
They have variable oxidation states
Why can transition elements be heterogenous catalyst
There are vacant d orbitals that are energetically accessible
Why can transition elements form complex ions
Transition elements have an ability to form dative bonds with ligands
Ligand
A species that donates its lone pair of electrons to form dative covalent bond to central metal ion
Monodentate
Ligand that donates one lone pair to form a dative covalent bond to the central metal ion
Bidentate
Ligand that donates two lone pair to form two dative covalent bonds to the central metal ion
Polydentate
Ligand that donates two or more lone pair to form many dative covalent bond to the central metal ion
Complex ion
A molecule or ion formed by a central metal ion surrounded by one or more ligands
Coordination number
The number of dative covalent bonds formed to the central metal ion
ligand exchange
One or more ligands in a complex ion is replaced by a new ligand
What colour is [Cu(H2O)6] 2+
Blue solution
What happens when you add an excess of NaOH to [Cu(H2O)6] 2+
blue precipitate is seen Cu(OH)2
Degenerate orbitals
the five d-orbitals with the same energy level in an isolated transition metal ion
Octahedral complex
3d orbitals aligned along x,y,z axes experienced greater repulsion (2 orbitals)
tetrahedral complex
3d orbitals aligned between x, y , z axes experienced greater repulsion (3 orbitals)
orbitals that experience greater electronic repulsion have
higher energy level
Why are transition elements coloured
During the complex ion formation, d orbitals are split into two different energy levels. A d-electron absorbs visible wavelength to be promoted from lower to higher d orbital. Colour seen is complementary to colour absorbed
Why does different complex ions have different colour
There are different energy gaps, between orbitals due to different ligands. d electrons absorb different visible wavelength to move to higher d orbital
The larger the energy gap
The higher the frequency of light absorbed
[Ni(H2O)6]2+ ion is green in colour. Explain the origin of the colour of this complex
d orbitals are split into two different energy levels. d electrons absorb red light to move from lower to higher d orbital. Green colour is seen as complementary colour
Why is cis-isomers polar
Their dipoles do not cancel each other out
Copper (I) and silver (O) salts are colourless. Explain why
d orbitals in Cu+ ad Ag+ are fully occupied. No electron can be promoted from lower to higher d-orbital
Why is trans-isomer non-polar
because their dipoles cancel one another
Kstab
Equilibrium constant for the formation of complex ion in a solvent from its constituent ions or molecules
Higher kstab value =
More stable
