What are s block elements?
The elements in which s subshell is occupied with electrons are called s-block elements. It consists of two groups of modern periodic table viz, group 1 and group 2 where the ground state electronic configurations of the last shells are ns1 and ns2. The outer most energy shell is represented as n. The elements of group 1 have ns1 configuration. They are called alkali metals. The elements of group 2 have ns2 configuration. They are called alkaline earth metals. Therefore, the electronic configuration of s block elements is generally expressed as ns1 – 2.
Characteristics of s block elements
- These metals are soft in nature
- They have low boiling and melting point
- Their ionization enthalpies are low
- They are highly reactive
- S block elements readily form univalent ions and bivalent ions.
- On igniting they impart colour to the flame.
- All s block elements except beryllium and lithium form ionic compounds.
Difference between alkali and alkaline earth metals
Some difference between alkali and alkaline earth metals are discussed below:
|Alkali metals||Alkaline earth metals|
|Very soft||Not too soft|
|Low melting point||High melting point|
|Highly basic hydroxides||Less basic hydroxides|
|Nitrates product obtained are oxygen and corresponding nitrates||Nitrates product obtained are oxygen and corresponding nitrogen dioxide|
|Has one electron||Has two electrons|
|Carbonates do not decompose||Carbonates decompose|
|Example: Francium, potassium, lithium, rubidium, sodium, caesium.||Example: Radium, strontium, magnesium, barium, calcium, beryllium.|
Properties of Alkaline earth metals:
Atomic Radii –
The atomic and ionic radii are large enough but smaller than alkali metals and increases down the group.
They have low ionization enthalpy but greater than group 1 elements and decreases down the group.
The hydration enthalpy of alkaline earth metals decreases with the increase in the size of metal ion down the group.
Properties of Alkali metals:
Atomic Radii –
The atomic, as well as ionic radii of alkali metals, increases down the group.
They have low ionization enthalpy and decrease down the group.
The hydration enthalpy of alkali metals decreases as the size of the ion increases.
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