Explanation Of S-Block (Group IA) Elements

S – Block

(Group IA Elements)

Group I A Elements:

Hydrogen (Atomic number - 1)

Lithium (Atomic number - 3)

Sodium (Atomic number - 11)

Potassium (Atomic number - 19)

Rubidium (Atomic number - 37)

Strontium (Atomic number - 55)

Francium(Atomic number - 87)

•  Elements of group IA and IIA are known as s - block elements.
•  Except Hydrogen all elements are metals.
•  Group IA consists of Hydrogen, Lithium, Sodium, Potassium, Rubidium, Cesium, Francium.
•  Group IIA consists of Beryllium, Magnesium, Calcium, Stratium, Barium, Radium.
•   IA elements (except Hydrogen) - Alkali metals.
•   IIA Elements  → Alkaline earth metals.
•  Have one electron in the outermost orbit.
•  By loosing the electron they form stable + 1 ion.
•  They are univalent and show + 1 oxidation state.

General periodic trends:

•  As we move from up to down the atomic radius increases.
• Order of radius size = H < Li < Na < Rb < Cs < Fr
• Ionization potential coming from top to bottom decreases.
• Density generally increases with an increase in atomic mass.
• Exception  → Potassium is expected to have more density than sodium but actually has less than sodium.
• Electronegativity from top to bottom decreases.
• Alkali metals along their individual periods have largest atomic radius.
• Mobility of ions increases down the group∴ Rb⁺ > K⁺ > Na⁺ > Li⁺ > H⁺  is the order of mobility of ions.
• Hydration enthalpy decreases down the group.
  ∴ H⁺ > Li⁺ > Na⁺ > K⁺ > Rb⁺  in case of hydration enthalpy.

⇒ Heating effects of carbonates of IA elements. 

(M = Na, K, Rb, Cs), (Exception Li₂CO₃ → Li₂O + CO₂)

⇒ All metal carbonates of IA except Li₂CO₃ have no effect on heating.

⇒ Heating effect of nitrates of IA elements.

(M = Na, K, Rb, Cs), (LiNO₃ → Li₂O + NO₂)

Flame Test:
Li → Crimson Red

Na →Yellow

K → Violet

Rb → Red Violet

Cs → Blue