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Group 1: Alkali metals Reaction of sodium (Na) and water Reaction of potassium (K) in water. The alkali metals (Li, Na, K, Rb, Cs, and Fr) are the most reactive metals in the periodic table - they all react vigorously or even explosively with cold water, resulting in the displacement of hydrogen.
Metal aqua ions are often involved in the formation of complexes. The reaction may be written as pM x+ (aq) + qL y− → [M p L q] (px-qy)+ In reality this is a substitution reaction in which one or more water molecules from the first hydration shell of the metal ion are replaced by ligands, L. The complex is described as an inner-sphere complex.
The alkali metals also react with water to form strongly alkaline hydroxides and thus should be handled with great care. The heavier alkali metals react more vigorously than the lighter ones; for example, when dropped into water, caesium produces a larger explosion than potassium if the same number of moles of each metal is used.
The order of reactivity, as shown by the vigour of the reaction with water or the speed at which the metal surface tarnishes in air, appears to be Cs > K > Na > Li > alkaline earth metals, i.e., alkali metals > alkaline earth metals, the same as the reverse order of the (gas-phase) ionization energies.
Alkali hydroxides are formed in the reaction between alkali metals and water. A typical school demonstration demonstrates what happens when a piece of an alkali metal is introduced to a bowl of water. A vigorous reaction occurs, producing hydrogen gas and the specific alkali hydroxide. For example, if sodium is the alkali metal:
Solvated electrons are involved in the reaction of alkali metals with water, even though the solvated electron has only a fleeting existence. [10] Below pH = 9.6 the hydrated electron reacts with the hydronium ion giving atomic hydrogen, which in turn can react with the hydrated electron giving hydroxide ion and usual molecular hydrogen H 2. [11]
A basic salt of an alkali metal or alkaline earth metal [2] (this includes Mg(OH) 2 (magnesium hydroxide) but excludes NH 3 ). Any base that is soluble in water and forms hydroxide ions [3] [4] or the solution of a base in water. [5] (This includes both Mg(OH) 2 and NH 3, which forms NH 4 OH.) The second subset of bases is also called an ...
Lithium oxide (Li 2 O) is the lightest alkali metal oxide and a white solid. It melts at 1570 °C. Sodium oxide (Na 2 O) is a white solid that melts at 1132 °C and decomposes at 1950 °C. It is a component of glass. Potassium oxide (K 2 O) is a pale yellow solid that decomposes at 350 °C.