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S-BLOCK NEET/AlIMS/JIPMER - Anmol Sharma
S-BLOCK INTRODUCTION The elements in which the last electron enters the outermost s-orbital are called s-block elements. . The group 1 and 2 of periodic table belong to the s-block Group 1 of the Periodic Table consists of the elements: lithium, sodium, potassium, rubidium, caesium and francium. Group 2 include beryllium, magnesium, calcium, strontium, barium and radium.
Group 1 (1) The Elements: are Li, Na, K, Rb, Cs Fr (Radioactive: ty2 of Fr233 21 minutes) group-I elements are called alkali metals because they form hydroxides on reaction with water, which are alkaline in nature. (2) Outer Electronic configuration: ns1 (3) Atomic and Ionic radii L1 < Na < K < Rb < Cs. Increase down the group, because value of n(principal quantum number) increases. (4) Density L < K < Na < Rb < Cs. (5) Ionization Energy Li> Na> K> Rb > Cs. As size increases, I. E. decreases down the group (so Cs have lowest I. P.) Note: This is self created content for educational purpose only
(6) Hardness and melting points/boiling points These metals are very soft and can be cut with a knife. Litium is harder than any other alkali metal The hardness depends upon cohesive energy M. P. Li Na> K> Rb> Cs B, P. Li > Na > K > Cs > Rb (7) Electropositive character or metallic character Alkali metals are strongly electropositive and metallic. Down the group electropositive nature increase so metallic nature also increases i.e., M M+ + e- 1 Metallic Nature : Electropositive character Li< NaKRb<Cs. Note: This is self created content for educational purpose only
(8) Oxidation state Show +1 oxidation state because by loosing one electron they get stable noble gas configuration (9) Photoelectric effect The phenomenon of emission of electrons when electromagnetic rays strikes against them is called photoelectric effect Alkali metal have low I. P. so show photoelectric effect. Cs and K are used in photoelectric cells Note: This is self created content for educational purpose only