METALLIC HYDRIDES - POLYMERIC HYDRIDES - BORDER LINE HYDRIDES
 
 
METALLIC HYDRIDES
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These are the hydrides of transition elements (except elements of group I-B and II-B).
In transition elements there are small empty spaces among the atoms. Hydrogen gas adsorbs in these empty spaces to produce non-stoichiometric hydrides or Interstitial hydrides which are known as metallic hydrides.
EXAMPLES
 
ZrH1.92 , TaH0.76 , PrH2.3 , TiH1.7
PROPERTIES
 

 

1) They do not follow stoichiometric rules.

2) They behave like pure metal.

3) Bonding between metal and hydrogen is metallic bond.

4) On heating they release hydrogen in atomic state.

5) They are solids.

6) There is no true chemical reaction between metal and hydrogen in these hydrides.

7) They are not true chemical compounds.

8) They are used as reducing agent in different processes.

POLYMERIC HYDRIDES
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Hydrides of Beryllium and Magnesium are known as polymeric hydrides. In polymeric hydrides a large number of (BeH2) or (MgH2) units are joined together by hydrogen bonding to produce long chain of (BeH2) or (MgH2) .
GENERAL REPRESENTATION
 
(BeH2)n
(MgH2)n
There properties are between ionic hydrides and covalent hydrides.
BORDER LINE HYDRIDES
 
Hydrides of the elements of I-B and II-B and (In) Indium and Thallium (Tl) are known as borderline hydrides.
EXAMPLES
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CuH2
ZnH2
TlH2
They have properties intermediate between covalent and metallic hydrides
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