GROUPS I AND II 129
(jroup 1 contdElement LiChlorides Hydrated
deliquescent
Na KAnhydrousRb CsHeat of formation increasingBromides
and
iodides
Soluble in
organic
solventsMelting point decreasingInsoluble in organic solventsHeat of formation increasingMelting point decreasingChlorides,
bromides and
iodides
Group IIElementFluorides
BeSoluble in
waterMgSparingly
^olnVilp in
waterCa SrInsoluble in waterBaCovalent
when
anhydrous.
Soluble in
organic solvents.
Hydrolysed
by waterSoluble in waterTHE OXIDES AND HYDROXIDES
The white solid oxides M^O and M"O are formed by direct union
of the elements. The oxides M! 2 O and the oxides MUO of calcium
down to radium have ionic lattices and are all highly basic; they
react exothermically with water to give the hydroxides, with acids
to give salts, and with carbon dioxide to give carbonates. For
example
Na 2 O + H 2 O -» 2NaOH
BaO + CO 2 -> BaCO 3
Magnesium oxide is almost inert towards water, but dissolves in