s -Block Elements

General Introduction, Electronic Configuration and Anamalous Properties


Electronic configuration of IA group elements:
H → 1s1
Li →[He]2s1
Na → [Ne]3s1
K → [Ar]4s1
Rb → [Kr]5s1
Cs → [Xe]6s1
Fr → [Rn]7s1
General formula is ns1
IA group elements are called alkali metals because these and their oxides reacts with H2O and produce alkalies

II A group elements is also called alkaline earth metals.
Electronic configuration of IIA group elements:
Beryllium → Be → [He]2s2
Magnesium → Mg → [Ne]3s2
Calcium → Ca → [Ar]4s2
Strontium → Sr → [Kr]5s2
Barium → Ba → [Xe] 6s2
Radium → Ra → [Rn] 7s2
General formula is ns2

General properties :
Density increases
Beryllium to calcium decreases and then increases
Be > Mg > Ca > Sr > Ba
Melting point and Boiling point :
II A > I A
   ↓
ns2 2e-
Hydration energy decreases from top to bottom
II A > I A
Flame test :
Be and Mg do not give flame test due to small size and strongly bounded by nucleus.
Ca → Brick red colour
Sr → Crimson red colour
Ba → Apple green colour.
Reducing nature (Decreases ↓)
I A > II A

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