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S block elements
What are S-Block Elements?

Elements for which the last electron or valence electrons enter the s-subshell are known as sblock elements
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The s-block
contains the elements of Groups 1 and 2 in the periodic table
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Highly reactive in nature, they do not exist in the free
state
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Group 1 elements have only one electron
in the valence shell while Group 2 elements have two electrons in their valence shell
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Therefore, they are highly
electropositive in nature
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The electronic configuration
of all alkali metals in the periodic table is shown below
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Due to this property, s-block
elements of Group 1 show comparable properties
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Based on these two factors, the properties of alkali metals can vary in the following
ways:
Size

The size of alkali metals increases while moving down the group because the
number of shells increases
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In
Group 1, lithium (Li) is the smallest and cesium (Cs) is the largest in size
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Alkali metals have only one electron in the s orbital
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So, their
first ionization energy is low
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After the removal of one electron, their oxidation state changes from
0 to +1
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M(g)→M(g)+ + e−M(g)→M(g)+ + e-

where M = Na, K, Li, Rb, CsM = Na, K, Li, Rb, Cs
When one electron is removed from the valence shell
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So, the second ionization energy is quite high
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As the shell number increases, the distance between the nucleus
and valence shell increases
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So, the removal of electrons from such atoms is easier
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Reducing Properties

Alkali metals act as extraordinarily strong reducing agents due to their ability to
lose electrons
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Reducing
nature is determined from the standard electrode potential values
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Li has the highest reduction potential value among the all-alkali metals
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Coloration to the Flame

They give out characteristic color when exposed to the flame
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But life in the excited state
is truly short
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This emitted
energy is the reason behind the coloration
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The atoms have significant
differences in the electronegativities, so the bond formed between them is ionic
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Examples of ionic compounds
are NaCl, LiCl, KCl, CsCl, etc
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They
are highly stable
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Chemical Properties of Alkali Metals

In the isolated state, they are highly reactive
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They have low ionization energies and are bigger in size
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1) Superoxide, oxides, and peroxides
When these elements are burned in the free air, they form oxides, peroxides, and
superoxide with the metal ions
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Na forms the peroxide
Na2O2, heavier elements form superoxide
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It has a –1 charge and it readily
combines with positively charged ions
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They are strong bases
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When it
is reacted with a strong acid, it forms salt and water as the products
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Li is small in size; it cannot
accommodate elements around itself
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It
decomposes when heated
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4) Solutions in liquid Ammonia
When alkali metals are dissolved in the liquid ammonia, they form a blue-colored
solution
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The solution has free
electrons, so it is paramagnetic in nature
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The Reaction between an alkali metal and liquid ammonia is shown
below:

Alkaline Earth Metals

Elements of group 2 are known as alkaline earth metals
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Their oxides are alkaline in nature and Earth word is given to
those which remain unchanged upon heating
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They are highly reactive
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They have two valence electrons in the s orbital
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So, electrons are
held loosely
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Atomic
Number

Electronic
Configuration

Beryllium
(Be)

4

[He]2s2

Magnesium
(Mg)

12

[Xe]2s2

Calcium
(Ca)

20

[Ar]2s2

Strontium
(Sr)

38

[Kr]2s2

Barium (Ba)

56

[Xe]2s2

Radium
(Ra)

88

[Rn]2s2

Element

As it is clear from the table
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So, they have similar chemical and physical properties
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Size

Alkali earth metals have a smaller radius than group 1 in the periodic table
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Due to this atomic radius
increases as moved down the group
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They
have 2 electrons in the s orbitals
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But they can lose two electrons from the subshell and form
M2+ ions
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After
ionization, the oxidation state of alkaline earth metals changes from zero to +2
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As moving down the group, the atomic size increases due to an increase in the
number of shells
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The nucleus does not have a stronghold at larger
distances
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So, Ionization
energy decreases down the group
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They are comparatively
smaller in size than alkali metals and have high hydration energies
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As moving down the group, the reduction potential values increase down the
group
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Coloration to the Flame

They have a smaller size than group 1
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They have high ionization energy values
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Element
Be

Color to the flame
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Mg

-

Ca

Brick Red

Sr

Crimson

Ba

Apple green

Ra

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Chemical Properties of Alkaline Earth Metals

Elements have a smaller size and increased nuclear charge
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The oxides formed by alkaline earth metals have a
covalent character
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Compounds of
metals are insoluble in water due to their covalent character
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Beryllium
hydride is quite a common example of metal hydride
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Carbides

When they are heated in the furnace in the presence of carbon, they result in the
formation of metal carbide with the chemical formula MC2
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It liberates ethene upon reacting
with water
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Magnesium sulfate has the chemical
formula MgSO4
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It is known as Epsom salt and is used as a purgative
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2H2O
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It is extensively used in industries



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