in this ppt discussing properties of alkaline earth metals

1. ALKALINE EARTH METALS
AMRUTHA T.K

3. EXRACTION OF ALKALINE EARTH
METALS

8. Occurrence of calcium
• The important ore of calcium are
• Calicite
• Marble
• Gypsum etc

9. Extraction of calcium
• The metal is extracted by the electrolysis of fused
calcium chloride
• Calcium chloride mixed with the 10% of calcium
fluoride in a graphite vessel using Fe cathode &
graphite anode

10. Occurrence of Sr
• Sr occur SrSO4 in the mineral Celestine
• Strontianite (SrCO3) etc
Extraction of Sr
• The metal is obtained by the electrolysis of fused
mixture of strontium chloride and ammonium
chloride using Fe is cathode and graphite is anode

11. Occurrence of Ba
• Ba occur BaCo3 in the mineral witherite
• BaSO4 in the mineral baryte etc
Extraction of Ba
• The metal is obtained by the electrolysis of fused
Barium chloride using Hg is cathode and graphite is
anode. The barium amalgam separated out the on
distilling mercury volatiles of living behind barium

12. Occurrence of Ra
• All the uranium mineral contain Ra in minute
quantity pitch blend and carnolite are the chief source
of Ra
Extraction of Ra
• The metal is obtained by the electrolysis of fused
Radium chloride using Hg is cathode and platinum,
iridium anode. The Ra amalgam separated out the on
distilling mercury volatiles of living behind Radium

13. FLAME COLOURISATION

14. •Like alkali metal salts, alkaline earth metal salts also impart
characteristic flame colouration.
•As we move down the group from Ca to Ba, the ionisation energy
decreases, hence the energy or the frequency of the emitted light
increases. Thus,
Ca Sr Ba
Brick red Crimson red Apple green
•Be and Mg because of their high ionization energies, however, do not
impart any characteristic colour to the bunsen flame.

15. SOLUBILITY IN LIQUID AMMONIA
•Like alkali metals, these dissolve in liquid ammonia
giving coloured solutions.
•The tendency to form ammoniates decreases with
increase in size of the metal atom (i.e., on moving
down the group
(please study the uses, properties ,reaction from
alkali metal slide)

16. BASIC STRENGTH OF OXIDES AND
HYDROXIDES
•BeO and Be(OH)2 are amphoteric while the oxides and hydroxides of other
alkaline earth metals are basic. The basic strength, however, increases from Be to
Ba as the ionisation energy of metal decreases down the group thus the order:
BeO < MgO < CaO < SrO < BaO and
Be(OH)2 < Mg(OH)2 < Ca(OH)2 < Sr(OH)2 < Ba(OH)2
•The basic character of hydroxides of group-2 elements is lesser than those of
group-1 hydroxides because of the larger size elements of latter than former
group.
•Aq. Ba(OH)2 is known as baryta water

17. REACTION WITH HYDROGEN
• Except Be, all other elements combine with hydrogen on heating to form hydride (MH2)
• The hydride of beryllium can be prepared indirectly by reducing beryllium chloride with lithium
aluminium hydride.
• BeH2 and MgH2 are covalent and polymeric whereas the hydrides of Ca, Sr and Ba are ionic and
monomeric in nature.
• CaH2 is also called hydrolith.
• All the hydrides react with water to evolve H2 and thus behave as strong reducing agents

18. Alkaline earth metals from calcium to barium react with all halogens to form solid ionic
halides with a definite crystal structure. Reactivity decreases from fluorine to iodine.
Beryllium halides are an exception with more covalent bonding because of the high
polarization of the small covalent ion on the electron cloud of the halogen anion as
indicated by the Fajan’s rule
In the gas phase, Beryllium halides exist as individual molecules and in the solid phase,
they form chains of Be-X.
Fluorides are insoluble in water. The solubility of other halides decreases with increase in
ionic size i.e. from Mg2+ to Ba2+. Halides are hygroscopic and have the water of
crystallization in their solid state (CaCl2.6H2O). Fused halides are used as dehydrating
agents.
HALIDES

19. CARBONATES AND BICARBONATES
The hydroxides react with carbon dioxide to carbonates.
M(OH) 2 + CO2 → MCO3 + H2O
Bicarbonates are soluble in water and exist only in solution.
Carbonates exist as solid and insoluble in water.
The solubility of carbonates decreases from Be to Ba.
In the presence of carbon dioxide, carbonates dissolve by
forming bicarbonates. Ionic character and the thermal stability of the
carbonates increases from Be to Ba

20. DIAGONAL RELATIONSHIP

21. DIAGONAL RELATIONSHIP OF Li WITH Mg
Li of group One resembles more with Mg of group two:

22. DIAGONAL RELATIONSHIP OF BERYLLIUM WITH ALUMINIUM
Beryllium of group two resembles more with Aluminum of group three:
Both beryllium and aluminium occur together in the mineral, “Beryl” 3BeO Al2O3 6SiO2
Both of them do not react with atmospheric oxygen and nitrogen.
Both of them do not react with water even at high temperatures.
They do not liberate hydrogen from acid. On treatment with concentrated nitric acid, they
become passive.
Both form polyvalent bridged hydrides of covalent nature.
Halides of both are polyvalent, bridged, and of low melting points. Halides are Lewis acids.
Water hydrolyzes both nitrides liberate ammonia.
Oxides and hydroxides of Be and Al are amphoteric. So, they react with acid as well base.
Both form carbide, that on hydrolysis yields Methane.
Carbonates of beryllium and Aluminum are unstable.

23. Macrocycles are often described as molecules and ions containing twelve or more membered
ring. Classical examples include the crown ethers, calixarenes, porphyrins, and cyclodextrins.
Macrocycles describe a large, mature area of chemistry
MACRO CYCLIC COMPOUND

24. WHAT ARE CROWN ETHERS?
Crown ethers are cyclic organic compounds containing ether groups.
They are ring structures that contain several ether groups.
These are named as crown ethers because when these compounds are bound to a metal ion, they
resemble a crown on a persons’ head.
The most common members of this group of ethers are oligomers of ethylene oxide. There are
tetramers, pentamers, hexamers, etc. depending on the number of ether groups present in the ring.
When naming the crown ether,
• the first number of the name refers to the number of atoms present in the compound
• the second number refers to the number of oxygen atoms in the compound.

25. Crown ethers can act as ligands and slightly bind with cations, forming complexes.
The lone electron pairs on oxygen atoms are used in forming these coordinate bonds.
The exterior of the ring is hydrophobic.
Crown ethers are useful in phase transfer catalysis because they are soluble in
nonpolar solvents.

26. WHAT ARE CRYPTANDS?
Cryptands are a group of organic compounds that contain ether groups and
nitrogen atoms.
These are either cyclic or non-cyclic structures.
 We can define them as bicyclic or polycyclic synthetic molecules.
The name of these compounds, cryptands, is given due to their ability to bind with
substrates that looks like they are in a crypt.
The structure of cryptands resemble the structure of crown ethers, but these are
more selective and strong when it comes to complex formation with cations

27. The most common cryptand is [2.2.2]cryptand, which has two oxygen atoms per
each of the three bridges between two nitrogen atoms in the molecule. Moreover,
cryptands have a high affinity towards metal cations such as potassium ion.
The interior cavity of the three-dimensional molecule is the binding site for cations.
When the complex is formed, we call it a cryptate.
 More importantly, cryptands can bind with cations through both nitrogen and
oxygen atoms.
However, the structure of these compounds enables them to show more selectivity
towards alkali metal cations

30. DIFFERENCE BETWEE CROWN ETHER AND CRYPTAND