Sum-to-Product Formulae

 Power-Reducing/Half Angle Formulae

 Double Angle Formulae

 Lithium forms monoxide, sodium forms

peroxide, the other metals form

superoxides. The superoxide   ion is

stable only in the presence of large cations

such as K, Rb, Cs.

 The oxides and the peroxides are colourless

when pure, but the superoxides are yellow or

orange in colour

 Lithium unlike other alkali metals forms

no ethynide on reaction with ethyne

 Lithium nitrate when heated gives lithium

oxide, Li₂O, whereas other alkali metal

nitrates decompose to give the

corresponding nitrite

 Thermal decomposition of (NH₄)₂BeF₄ is the

best route for the preparation of BeF₂

 The alkaline earth metals burn in oxygen to form the

monoxide, MO which, except for BeO, have

rock-salt structure

Why does the solubility of alkaline earth

metal hydroxides in water increase down

the group?



Solution



Among alkaline earth metal hydroxides,

the anion being common the cationic

radius will influence the lattice enthalpy.

Since lattice enthalpy decreases much

more than the hydration enthalpy with

increasing ionic size, the solubility

ncreases as we go down the group.

Why does the solubility of alkaline earth

metal carbonates and sulphates in water

decrease down the group?

Solution

The size of anions being much larger

compared to cations, the lattice enthalpy

will remain almost constant within a

particular group. Since the hydration

enthalpies decrease down the group,

solubility will decrease as found for

alkaline earth metal carbonates and

sulphates.