9. Physical properties of dihydrogen Hydrogen is a colorless, odorless and a tasteless gas Hydrogen is highly combustible Hydrogen is lighter than air Hydrogen is insoluble in water
10. The binary compounds of hydrogen with other elements are called hydrides
11. Ionic hydrides or Saline hydrides are binary compounds of hydrogen with s- block elements which are highly electropositive
12. Covalent or molecular hydrides are binary compounds of hydrogen with elements of comparatively high electronegativity such as p-block elements
13. Covalent hydrides are classified as electron rich, electron deficient or electron precise hydrides
Electron rich hydrides have excess electrons than required to form normal covalent bonds. Excess electrons are present as lone pairs. Examples of this are hydrides of group 15, 16 and 17 such as ammonia, water etc.
Electron deficient hydrides do not have sufficient number of electrons to form normal covalent bonds. Examples of this are hydrides of group 13
Electron precise hydrides have required number of electrons to write the conventional Lewis structure. Elements of group 14 like carbon, silicon etc. form these types of hydrides
14. Metallic hydrides or Interstitial hydrides are the compounds of hydrogen with transition metals of group 3,4,5 of d-block, Cr metal of group 6, f-block element
15. Since the composition of metallic hydrides does not correspond to simple whole number ratio they are also called non-stoichiometric hydrides
16. Due to high polarity, water dissolves most of the polar substances
17. Due to hydrogen bonding water has high boiling point and high heat of vaporization
18. Density of water is more than that of ice