![]() Heat energy is produced but not enough to cause melting or a flame. Fizzing is produced and the piece of metal dissolves slowly. When lithium is added to the water it moves slowly around on the surface. However, the reactivity of the alkali metals with water changes as you go down through the group. Potassium reacts with water to produce potassium hydroxide and hydrogen gas, as shown by the equation:Īs can be seen by the equations for the reactions, all of the alkali metals react with, and dissolve into, water to form strongly alkaline solutions of metal hydroxides and hydrogen gas. Sodium reacts with water to produce sodium hydroxide and hydrogen gas, as shown by the equation: Lithium reacts with water to produce lithium hydroxide and hydrogen gas, as shown by the equation: For example, sodium atoms become sodium ions in solution when a piece of sodium is added to water: This is why the group 1 metals are known as the alkali metals.ĭuring these reactions, the alkali metal atoms lose electrons and form metal ions in solution. If universal indicator solution was added to the solution formed, a dark blue or purple colour would be observed, showing that the solution formed was strongly alkaline. The pieces of metal dissolve into the water to produce a solution. If this gas was tested with a lit splint, a squeaky pop sound would be heard, showing that the gas was hydrogen. This fizzing shows that a gas is produced. They move around on the surface of the water and fizzing can be observed. When the alkali metals are added to water they start to react straight away. This means that when small pieces of them are added to water, they will float. The alkali metals all have densities which are lower than that of water. As you descend through group 1, the elements become more reactive with oxygen. These observations show that there is a trend in reactivity in group 1. Sodium becomes duller faster than lithium, and potassium becomes duller much faster than sodium. This is evidenced by the freshly cut surface of the metal becoming duller much faster. Sodium reacts with the oxygen in the air to form sodium oxide:Īnd potassium reacts with the oxygen in the air to form potassium oxide:Īs you move down through the group, the speed at which the layer of metal oxide is formed increases. For example, lithium reacts with the oxygen in the air to form lithium oxide: ![]() The metal becomes tarnished and a layer of metal oxide is formed. This surface quickly becomes dull as the metal reacts with the oxygen in the air. When alkali metals are first cut, their surface is very shiny. We will now explore the reactions of alkali metals with oxygen and water in more detail. They all react with oxygen and water in a similar manner, form colourless solutions of the metal ions, and react with non-metals to produce white or colourless ionic compounds. Alkali metals all show the same chemical properties. ![]()
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