Trends In The Variation Of Properties Of S-Block Elements

S-block-elements

In a modern periodic table of elements Group, 1 and Group 2 are called the S-block elements. It is observed that the physical and chemical properties of these elements changes in a particular trend as the atomic number of the elements increases. Changes in the various properties of the group are as mentioned below:
1. Atomic and ionic radii: When a modern periodic table is observed it is seen that the size of the alkali metals is larger compared to other elements in a particular period. As the atomic number increases the no. of electrons increases along with the addition of shells. On moving down the group the atomic number increases. As a result, the atomic and ionic radius of the alkali metals increases.2. Ionization enthalpy: As we go down the group the size of the atoms increases due to which the attraction between the nucleus and the electrons in the outermost shell decreases. As a result, the ionization enthalpy decreases. The ionization enthalpy of the alkali metals is comparatively lesser than other elements.

Atomic and ionic radii of S group elements

2. Ionization enthalpy: As we go down the group the size of the atoms increases due to which the attraction between the nucleus and the electrons in the outermost shell decreases. As a result, the ionization enthalpy decreases. The ionization enthalpy of the alkali metals is comparatively lesser than other elements.
3. Hydration enthalpy: As the ionic sizes of the elements increases the hydration enthalpy decreases. Smaller the size of the ion the hydration enthalpy is high as the atom has the capacity to accommodate a larger number of water molecules around it due to high charge/radius ratio and hence gets hydrated.
4. Physical properties:
• The density of the alkali metals increases down the group. Exception: the density of potassium is less than the density of sodium.
• The alkali metals have a low melting and boiling point due to the weak metallic bonding.
• Alkali metals and its respective salts have the capability to impart color to the oxidizing flame due to the heat generated from the flame which excites the valence electrons from one energy level to another energy level. This helps in the detection of alkali metals during the flame test.
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The hydration energy of Mg2+ is greater than that of