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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 alkali metals (lithium, sodium, potassium, rubidium, caesium, and francium) are the most homogeneous column of elements in the periodic table, exhibiting very clear periodic trends. All of them are soft and extremely reactive metals, readily giving up their sole valence electron to form cations.
In 1860, the unexpected appearance of sky-blue and dark red was observed in spectral emissions by Robert Bunsen and Gustav Kirchhoff, leading to the discovery of two alkali metals, caesium and rubidium (dark red). [4] [1] Today, this low-cost method is used in secondary education to teach students to detect metals in samples qualitatively. [2]
The most reactive metals, such as sodium, will react with cold water to produce hydrogen and the metal hydroxide: 2 Na (s) + 2 H 2 O (l) →2 NaOH (aq) + H 2 (g) Metals in the middle of the reactivity series, such as iron , will react with acids such as sulfuric acid (but not water at normal temperatures) to give hydrogen and a metal salt ...
Notable examples include alkali metals, lithium through caesium, and alkaline earth metals, magnesium through barium. Some water-reactive substances are also pyrophoric, like organometallics and sulfuric acid. The use of acid-resistant gloves and face shield is recommended for safe handling; fume hoods are another effective control of such ...
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.
In the periodic table, potassium is one of the alkali metals, all of which have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge (which combines with anions to form salts). In nature, potassium occurs only in ionic salts.
In chemistry, an alkali (/ ˈ æ l k ə l aɪ /; from the Arabic word al-qāly, القلوي) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0.