THE s-BLOCK ELEMENTS

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299THE s- block ELEMENTSThe s- block ELEMENTS of the Periodic Table are those inwhich the last electron enters the outermost s-orbital. Asthe s-orbital can accommodate only two electrons, twogroups (1 & 2) belong to the s- block of the Periodic 1 of the Periodic Table consists of the ELEMENTS :lithium, sodium, potassium, rubidium, caesium andfrancium. They are collectively known as the alkali are so called because they form hydroxides onreaction with water which are strongly alkaline in ELEMENTS of Group 2 include beryllium, magnesium,calcium, strontium, barium and radium. These elementswith the exception of beryllium are commonly known asthe alkaline earth metals.

THE s-BLOCK ELEMENTS 301 Property Lithium Sodium Potassium Rubidium Caesium Francium Li Na K Rb Cs Fr Atomic number 3 11 19 37 55 87 Atomic mass (g mol–1) 6.94 22.99 39.10 85.47 132.91 (223) Electronic [He] 2s1 [Ne] 3s1 …

  Block, Elements, Block elements