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
Li → Crimson Red
Na →Yellow
K
→ Violet
Rb → Red
Violet
Cs → Blue