The Alkali Metals - A Brief Outline

Neutron absorption Thermal neutron capture cross section 2.2 barns 

The elements in group 1 are hydrogen and the alkali metals lithium li, sodium Na, potassium K, rubidium Rb, cesium Cs and francium Fr. The last one, francium, was discovered in 1939 by Marguerite Percy in Paris. It will be described in Chapter 52 The Radioactive Elements. The others wiU be treated in this and the following two chapters. 

The elements Li-Cs are aU similar but also show important differences. Their electron shells have a single s-electron in the outermost orbit, and they all form univalent ions in water solution. With water the metals react vigorously - almost explosively -with formation of hydroxides. Being the smallest of the alkali metal atoms, lithium has its Is-electron near the core and so has the highest ionization energy. In fact it is less reactive than the other alkali metals and more like magnesium. The big cesium atom on the other hand is easiest to ionize (oxidize) and is, as a consequence, the most reactive of all metals. 

Flame color Carmine Yellow Violet Bluish red Blue 

Nowadays it is quite clear that the alkali metals sodium and potassium are the base for two groups of chemicals, alkalis and nitrates  

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