Chemistry of alkali and alkaline earth metals and halogen compounds including their Pharmaceutical applications.

1. Alkaline Earth Metals: Group II
Md. Imran Nur Manik
Lecturer, NUB

2. Group 2 Elements
Sr
Ba
Ra
Ca
Be
Mg
Alkaline metal:
ns2
12+
Mg

3. Group II A of the long form of the periodic table consists
of six elements which are: Breyllium (Be), Magnesium
(Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and
Radium (Ra).
The oxides of the three metals viz., Ca, Sr and Ba were
known much earlier than the metals themselves and
were called alkaline earths, since they were alkaline in
character and occurred in nature as earths [lime (CaO),
strontia (SrO) and baryta (BaO)]. Later, when Ca, Sr and
Ba were discovered, they were named alkaline earth
metals.

4. BERYLLIUM
MAGNESIUM
CALCIUM
STRONTIUM
BARIUM
RADIUM
Group 2 Elements

5. Element Color Element Color
Li Scarlet Be －
Na Yellow Mg －
K Lilac Ca Brick-red
Rb Red Sr Crimson
Cs Blue Ba Apple-green
The Flame Color:
Group 2 Elements

6. The alkaline earth metals have inert gas configuration in
the core and ns2 electron in the outermost shell.
These configurations show that the ultimate shell of these
elements has two s-electrons (s2 electrons) while the
penultimate shell contains eight (s2p6 electrons.) When
the two s-electrons of the valence-shell are lost, alkaline
earth metals are converted into M2+ ions which have inert
gas configuration. Since the additional electron enters the
ns-orbital, these elements are called s-block elements.
Element Atomic number Electronic
structure
Valence electron
Be 4 [He] 2s2 2s2
Mg 12 [Ne] 3s2 3s2
Ca 20 [Ar] 4s2 4s2
Sr 38 [Kr] 5s2 5s2
Ba 56 [Xe] 6s2 6s2
Ra 88 [Rn] 7s2 7s2

7. 1. Nature:
These elements all are metals.
2. Physical state:
These elements have a greyish white lustre when freshly
cut and are malleable and ductile.
3. Atomic volume, atomic and ionic radii:
There is an increase of atomic and ionic radii as we move
from Be to Ra.
Elements Be Mg Ca Sr Ba Ra
Atomic Volume(c.c) 4.90 13.97 25.9 34.54 36.7 38.0
Atomic radii(Aº) 0.96 1.36 1. 74 1.91 1.98 2.20
Ionic radii(Aº) 0.31 0.65 0.99 1.13 1.35 1.52

8. PHYSICAL PROPERTIES CONT….
4. Ionization potential: The 1st and 2nd ionization
potentials of these elements decrease with the increase of
atomic radii from Be to Ba. However, both these values for
Ra are slightly higher than those of Ba.
5. Density: Like alkali metals the density of alkaline earth
metals also decreases down the order but in an irregular
manner due to difference in crystal structure of these
elements.
Elements Be Mg Ca Sr Ba Ra
Ionisation
energies
(KJ/mole)
I1 899.5 737.7 589.8 549.5 502.9 509.4
I2 1757.1 1450.7 1145.4 1064.3 965.2 979.06
Elements Be Mg Ca Sr Ba Ra
Density
(gm/cm3)
1.86 1.75 1. 55 2.60 3.59 6.0

9. Why alkaline earth metals are denser than alkali metals?
Comparing with the alkali metals is denser than alkaline earth metals in the
same period. This is due to the fact that , the elements of group II A are packed
more tightly due to the greater nuclear charge and smaller size.
6. Electropositive character: The alkaline earth metals
show electropositive character which increases from Be to
Ba.
M → M2+ + 2e-
Since the ionization energies of these metals are higher
than alkali metals, they are not strongly electropositive as
the alkali metals.
7. Electronegativity: These metals have small
electronegativity which decreases from Be to Ra.
PHYSICAL PROPERTIES CONT….
Elements Be Mg Ca Sr Ba Ra
Electronegativity 1.5 1.20 1.0 1.0 0.90 0.97

10. PHYSICAL PROPERTIES CONT….
8. Melting and boiling point: The melting and boiling points of
alkaline earth metals do not show any regular trend. They are,
however, higher than alkali metals. This is because of two valence
electrons and they are strongly bonded in the solid state than alkali
metals.
9. Colouration to the flame: In flame test, their electrons absorb
energy and excited to higher energy levels. When returning to lower
energy level, they give out extra energy which appears as visible light
of characteristic colour as shown below:
Beand Mg do not giveany colour to the flame.
10. Conductivity: Like alkali metals they are also very good
conductor of heat and electricity.
Elements Be Mg Ca Sr Ba Ra
Melting Point (ºC) 1280 651 851 776 710 960
Boiling Point (ºC) 1500 1100 1487 1366 1537 1150
Elements Ca Sr Ba
Colour of the flame Brick red Crimson red Apple green

11. 1. Reducing property: Alkaline earth metals have two electrons in
their valence shell. Due to large size they are comparatively easily
oxidised to M2+ ions. They are, therefore, strong reducing agents.
2. Reaction with oxygen: The alkaline earth metals react readily on
heating with O2 to form oxides, MO.
2M + O2 → 2MO
The peroxides of heavier metals (Ca, Sr, Ba etc.) can be obtained on
heating the normal oxides with O2 at high temperature.
2BaO + O2 2BaO2
3. Reaction with hydrogen: Ca, Sr and Ba react with H2 when
heated to produce crystalline metal hydrides. These hydrides react
readily with water to give hydrogen.
MH2 + 2H2O → M(OH)2 + 2H2

12. Magnesium oxide
2Mg (s) + O2 (g) 2MgO (s)
① burns very vigorously
② bright white flame
③ white solid produced
a. in the air b. in oxygen
Group 2 Elements

13. 4. Reaction with nitrogen: These metals form nitrides on heating in
presence of nitrogen which are hydrolysed by H2O to give ammonia.
3M+N2 → M3N2
M3N2+6H2O → 3M(OH)2 + 2NH3
5. Reaction with water: The alkaline earth metals readily react with
water giving off hydrogen and forming metal hydroxides.
M +2H2O → M(OH)2 + H2
Be and Mg do not react readily with water due to their low reactivity.
Be does not react even at elevated temperature. Mg reacts only with
steam.
6. Reaction with halogen: The alkaline earth metals directly react
with halogen to give metal halides.
M + X2 → MX2, X = F, Cl, Br, I

14. Similarities: The alkali and alkaline earth metals have quite a good deal
of resemblance in their properties. The points of similarity are:
Like alkali metals, alkaline earth metals are electropositive and have
great chemical activity.
The electropositive nature continuously increases from beryllium to
radium in the second group, as in the first group from lithium to
caesium.
They do not occur freely in nature.
Both are extracted by electrolytic method from their salts such as
chlorides.
Both are soft and silvery white in untarnished condition and very light.
React with water to give hydroxides and hydrogen (gas).
Their hydrides produce strong base with water.
NaH + H2O → NaOH + H2
CaH2 + 2H2O → Ca(OH)2 + 2H2
They have strong reducing property and forms ionic compounds.
They react with water or oxygen with readiness and show much activity
towards other substances.

15. Dissimilarities: The points of the contrast between the alkali and alkaline
earth metals arise mainly due to the presence of 2 valence electrons in
the case of alkaline earth metals and 1 valence electron in the case of
alkali metals.
Sl. Features Alkaline Earth Metals (AKM) Alkali Metals (AM)
01. Hardness More harder Less harder
02. Softness Less soft More soft than AKM
03. Heaviness More heavier Less heavier
04. Melting & Boiling pints More than AM Less than AKM
05. Density Greater Lesser
06. Basic character Less basic More basic
07. Size Smaller than AM Larger than AKM
08. Reducing property Lower than AM Higher than AKM
09. Oxides and
Hydroxides
More covalent in nature Less covalent in nature
10. Reaction with water Ca,Sr & Ba react less vigorously All AM react more vigorously
11. Solubility in water
Sulphates, carbonates and
phosphates of AKM are insoluble
in water
AM are soluble in water except
Li2CO3 and Li3PO4 which are
insoluble
12. Polarizing capacity Greater than AM Lower than AKM

16. Uses of alkaline earth metals
Magnesium (Mg):
It is the second most common cation in intracellular fluid.
FUNCTION:
1. Magnesium is needed for DNA repair.
2. It moderates cellular differentiation and proliferation and
improves tissue sensitivity to circulating insulin.
3. It is a component of enzymes required for the synthesis of
adenosine triphosphate (ATP) and the release of energy
from ATP.
4. It is also a component of enzymes involved in muscle
contraction and protein synthesis.
5. Decreased magnesium in the blood is called
hypomagnesemia. Clinically, it is accompanied by
increased neuromuscular irritability.

17. Uses Cont……
1. MgO: MgO is used
1. As antacid
2. In Mg deficiency
3. As an universal antidote
4. As an ingredient of zinc phosphate cellulose.
2. Mg(OH)2 : Mg(OH)2 is used
1. In high dose as a laxative.
2. Usually as a non-systemic antacid.
3. Prophylactically in stress induced ulcer.
4. As soap suspending and emulsifying agent.
3. Magnesium tri-silicate: It is used
1. As gastric antacid.
2. In drug toxicity

18. 4. Magnesium tri-silicate hydrated [Mg2Si3O8.2H2O]
It acts as
1. Suspending agent without the help of any other compound.
2. Thickening agent in the production of chocolate
3. 5. 7-8.5% Mg(OH)2 is called milk of magnesia and is used
as laxative.
6. MgSO4
1. In the treatment of eclampsia as an intravenous bolus and
a continuous infusion of magnesium sulfate are
administered.
2. A soluble salt of magnesium, is used parenterally in clinical
medicine to treat, e.g., hypomagnesemia and torsade de
pointes.
7. MgCO3 : It is used
1. As an antacid and mid laxative.
2. As an additive in tooth & face powder.
Uses Cont……

19. Calcium (Ca)
Ca is the major component of bone marrow. Bone matrixis made of
calcium carbonate, calcium phosphate, and collagen fibres.
FUNCTION:
1. Calcium is important for blood clotting, enzyme activation, and acid-
base balance;
2. It gives firmness and rigidity to bones and teeth; and
3. It is essential for lactation, the function of nerves and muscles
including heart muscle, and maintenance of membrane
permeability.
EXCESS: Hypercalcemia can cause constipation, renal stones, cardiac
arrhythmias, cardiac arrest, and depressed brain function (e.g., lethargy
or coma). High serum calcium levels are usually the result of either
hyperparathyroidism or metastatic cancer and may be reduced with
hydration, diuresis, corticosteroids, or bisphosphonate drugs like
pamidronate.
Uses Cont……

20. Uses Cont……
Calcium chloride (CaCl2.2H2O): It is used to raise the calcium content of
the blood in disorders such as in hypocalcemic tetany, calcium channel
blocker, or beta blocker overdose.
Calcium hydroxide (Ca(OH)2): It is used as an astringent applied to the
skin and mucous membranes.
Calcium sulphate (CaSO4): It is used
1. As diluent in tablet.
2. As plaster cast in the plaster of broken bone.
Calcium disodium edetate: It is used to treat poisoning caused by
metals.
Calcium gluconate: It is used to treat hypocalcemia, calcium channel
blocker, or beta blocker overdose.
Calcium glycerophosphate: It is used as a dietary supplement and in
formulating drugs.
Calcium tungstate: A fluorescent material used for radiological imaging.

21. Which one of the following equations represents the
reaction that occurs when calcium nitrate is heated
strongly?
A. Ca(NO3)2 → Ca(NO2)2 + O2
B. 2Ca(NO3)2 → 2CaO + 4NO2 + O2
C. Ca(NO3)2 → CaO + N2O + 2O2
D. 3Ca(NO3)2 → Ca3N2 + 4NO2 + 5O2
E. Ca(NO3)2 → CaO2 + 2NO2
√
Group 2 Elements

22. Which one of the following elements is likely to have
an electronegativity similar to that of aluminium?
A. Barium
B. Beryllium
C. Calcium
D. Magnesium
E. Strontium
√ diagonal relationship
Group 2 Elements

23. Compounds of Group II Elements
coins cosmetics
pipeShip

24. Compounds of Group II Elements
Hard water: Ca2+, Mg2+, SO4
2-, Cl-
Soft water: Ca2+, Mg2+, HCO3
2-
Ca2+(aq) + SO4
2-(aq) → CaSO4(s)
“temporary hardness”
“permanent hardness”
Ca2+ (aq) + 2HCO3
ˉ(aq) → CaCO3(s) + CO2(g) + H2O(l)
Mg2+ (aq) + 2HCO3
ˉ(aq) → MgCO3(s) + CO2(g) + H2O(l)
Δ
Δ

25. Compounds of Group II Elements
A number of methods can be used for softening water:
♦ Boiling removes temporary hardness, but is expensive.
♦ Calcium hydroxide is cheap and can be added to precipitate out
temporary hardness as calcium carbonate.
Ca(HCO3)2(aq) + Ca(OH)2(s) → 2CaCO3(s) + 2H2O(l)
♦ Sodium carbonate may be added to precipitate out calcium or
magnesium ions.
Mg2+ (aq) + Na2CO3(aq) → MgCO3(s) + 2Na+(aq)
♦ Use ion exchange resins: plastic beads which contain sodium ions.