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1
BONDING OF PERIOD 3 CHLORIDES
NaCl , MgCl – high conductivity in molten state
-‐ giant ionic
AlCl3(s)/ Al2Cl6 (g) – poor conductivity in molten state
-‐ molecular covalent
SiCl4, PCl5(s),PCl3(l), S2Cl2 , Cl2 – no conductivity
-‐ molecular covalent
* Transition from ionic to covalent is earlier than
corresponding oxide because chlorine is less electro – ve
than oxygen
...
e
Aluminium oxide is ionic but aluminium chloride is
covalent
REACTION OF PERIOD 3 CHLORIDES WITH WATER
1
...
) as Cl is simultaneously oxididized and
reduced
...
Hydration of Ionic Chloride
Metallic elements form ionic chlorides, which b reak up
their lattice structure when dissolved – become
hydrated; ions separated and surrounded b y water:
+ve ions attracted to p artially charged negative oxygen
atom
-‐ve ions attracted to p artially charged positive hydrogen
atom
NaCl à Na+ + Cl-‐
* Resulting solution contain free ions, therefore conduct
electricity
3
...
* Produce CO2 when added to sodium carbonate
Hydrolysis of silicon and phosphorus chlorides
a) Silicon chloride: react with water to produce HCl and
silicon d ioxide (insoluble)
SiCl4 + 2H2O à SiO2 + 4HCl
b) Phosphorus chlorides : produce acidic solution due to
formation of HCl and phosphoric cid
Liquid phosphorus (III) produce phosphoric (III) acid
PCl3 + 3H2O àH3PO3 + 3HCl
Solid phosphorus (V) chloride produces phosphoric (V)
acid
PCl5 + 4H2O à H3PO4 + 5HCl
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Characteristics Properties
of Transition Elements
Electron Configuration
Physical Properties
Chemical Properties
-‐
-‐
-‐
-‐
-‐
d-‐block elements have many half-‐filled 3d
orbitals
Across the block, decrease in atomic radii
is small because of small increase in
effective charge experienced by outer 4s
Increase in nuclear charge due to added
protons is offset by the addition of
electron in the inner 3d sub-‐level
This is why they can form alloys, because
the atoms can be replaced easily without
disruption to the solid structure
Small range in first ionization energies is
caused by small increase in effective
nuclear charge
-‐ Properties:
a) High electrical and thermal
conductivity
b) High melting point
c) Malleable (shape)
d) High tensile strength (stretch)
e) Ductile (drawn into wires)
-‐ Why
• Strong metallic bonding
• Delocalised electron
...
Why Scandium and Zinc are Not Transition Metals
Because of their electronic configuration
...
Properties 1 : Why variable oxidation number?
-‐ Because of successive ionization energies
-‐ Example: Ca & Ti,
(s-‐block) Ca : 1s2 2s2 2p6 3s2 3p6 4s2
(d-‐block) Ti : 1s2 2s2 2p6 3s2 3p6 3d2 4s2
-‐ For Ca3+, there is jump in ionization energy for 3rd electron because have
to remove from 3p orbital, which is far from 4s
...
-‐ For titanium( d-‐blocks ) , successive ionization energy is more gradual
...
Large jump occur between
4th and 5th ionization energy, so does not form +5 state
...
Properties 2 : Form Complexes
Ligands : at least one atom with a lone pair of electron to form dative
bond with central ion
Why can form? : Due to relatively high charge and small size of transition
metal ions – can attract the lone pair of ligands
...
Properties 3 : Form Colored Compounds
Why? : Their ions absorb some the colors that made up white light
...
After that ,
decreases -‐1
...
•
d-‐orbitals in an isolated transition metal atom is degenerate (
have same energy)
However, ligand’s lone pair of electron form electric field in
complex
Therefore, the d-‐orbital split into 2 sub levels
When light passed through a solution of the complex, one 3d
electrons will be excited from the lower to the higher energy sub-‐
level
...
Therefore, light of the
complementary colour (ex: purple) will be transmitted and visible
...
nuclear charge hence the identity of central ion
2
...
number of d electrons presence and hence the oxidation no of central
ion
4
...
Properties 3 : Act as Catalyst
Heterogenous Catalysis – catalyst in different state from the reactants
-‐ Due to ability of transition metal to use 3d and 4s electrons to form
weak bonds to small reactant molecules
...
Iron (Fe) in Haber process
N2 + 3H2 = 2NH3
2
...
Palladium (Pd) and platinum (Pt) in catalytic converters
4
...
V2O5 in the Contact process
Homogenous Catalysis – catalyst in same state as the reactants
-‐ Due to ability to show variable oxidation states – effective in redox
reactions
1
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Fe2+ ions
surrounded by 4 nitrogen atoms
...
2
...
Octahedral
...
Needed for RBC production and healthy nervous system