Periodicity Flashcards
What is melting ?
It involves breaking the lattice structure of a solid.
Define disproportionation.
It is the simultaneous reduction and oxidation of the same species.
Define amphoteric.
Having both basic and acidic properties.
Define electronegativity.
The measure of an atom’s ability to attract bonding electrons towards itself in a covalent bond.
How does the size of the electron cloud affect the covalent character of a compound ?
The bigger the electron cloud, the more polarisable the anion will be and thus the greater will be the covalent character.
Why do elements diagonal to each other have similar properties despite different valencies ?
They have similar electropositivity/electronegativity and similar charge density.
What affects the enthalpy change of lattice formation ?
The charge of and size of ions. As ionic radius decreases and ionic charge increases, the ionic compounds get more stable.
Define transition element.
An element that forms at least one compound with an incomplete d sub-shell.
What are the physical properties of transition elements ?
- First row is only metals.
- Little change in atomic/ionic radius and first IE.
- Successive IE shows a steady increase instead of sudden jump because 3d and 4s orbitals have similar energies.
- Hard and dense (small size + closely packed).
- High m.p (strong metallic bonding).
- good conductors (mobile electrons).
Why do transition elements have similar physical properties ?
- Similar physical properties due to little difference in ENC –> each electron enters the penultimate 3d shell but the additional proton is partly shielded from the 4s electrons due to the additional 3d electron.
Define complex ion.
When a central metal atom/ion is bonded to surrounding anions or molecules (ligands) by dative bonds.
Define ligands.
Molecules/anions with a least one lone pair of electrons which can be used to form dative bonds with a transition metal atom/ion.
Define coordination number.
The number of dative bonds formed by the transition metal atom/ion with the ligand in the complex.
Coordination number (C no) and shape of complex ion.
C no : 2 Shape : linear
C no : 4 Shape : tetrahedral
C no : 6 Shape : octahedral
Define d-d splitting.
In the presence of ligands, the set of degenerate 3d orbitals of transition metal is split into 2 groups with slightly different energy.
Define d-d transition.
When 3d electrons from the lower energy group are promoted to the higher energy group, a photon of light from the visible region in the EMS is absorbed.
Colour of Cr 2+
Blue
Colour of Cr 3+
Green
Colour of Cr2O4 (Dichromate VI)
Orange
Colour of Mn 2+ (aq)
Pale pink
Colour of MnO2 (s)
Black
Colour of MnO4 - (aq) (Manganate VII)
Purple
Colour of Fe 2+
Green
Colour of Fe 3+
Yellow
Colour of Fe(OH)2 (s)
Green ppt
Colour of Fe(OH)3 (s)
Red brow ppt
Colour of Cu2O (s)
Black ppt
Colour of Cu 2+
Blue
Colour of Cu(OH)2 (s)
Light blue ppt
Colour of [CuCl4]^2- (aq)
Yellow
Colour of [Cu(H2O)2(NH3)4]2+ (aq) or [Cu(NH3)4]2+
Dark blue
What is Diamagnetism
Occurs when elements has no unpaired electrons, therefore are weakly repelled in a magnetic field.
What is paramagnetism
Occurs when an element has one or more unpaired electron. They are attracted by an external magnetic field. Paramagnetism increases with an increase in the number of unpaired electrons.
What is crystal field theory
This theory states that the properties of complex ions are caused by the splitting of the d orbitals into 2 sets of different energies.
