You are very unlikely to come across these in a school lab. You would not be expected to know about these at this level. The video mentions three oxides of potassium being formed - potassium oxide, K 2O, potassium peroxide, K 2O 2 and potassium superoxide, KO 2. The second one shows it burning in oxygen. The first video just shows a piece being cut. Potassium is similar to sodium, but softer and more reactive. If you are ever asked, just talk about sodium oxide being formed, and give the simple equation: The next video shows this happening.Ĭhemistry gets a bit more complex now, because the sodium reacts to form two oxides - sodium oxide, Na 2O, and sodium peroxide, Na 2O 2.Īt this level you are unlikely to need to know about the formation of the peroxide. Sodium burns in oxygen with an orange-yellow flame. Sodium and the rest of the group only react with oxygen and not nitrogen. Sodium is softer than lithium and tarnishes faster when it is cut. At this level, you are unlikely to need to know about the nitride, but you could be expected to write an equation for the formation of the oxide. You get a mixture of lithium oxide and lithium nitride. Flame colours can be used to help to identify some metals in compounds.īut when lithium burns, it burns with a while flame. We call these colours "flame colours" and the compounds of some metals have this sort of effect on flames. The red flashes when the lithium is heated in air are due to lithium compounds affecting the colour of the flame. Lithium is unique in Group 1 because it reacts with nitrogen in the air as well as oxygen. The sequence of videos coming up shows this happening, and also illustrates the way the metals are stored. Reactions of the Alkali Metals with air or oxygenĪll the metals react with gases in the air. Rubidium and caesium are more normally found in sealed glass phials under an inert atmosphere of argon. You are most likely to need to know this in their reactions with water.Īll of these metals react with air and water, and so you will find the commonest of them (lithium, sodium and potassium) stored under oil. Rubidium and caesium are both a bit denser than water, and so sink in water. Lithium, sodium and potassium are all less dense than water, and so float on water. Notice that caesium melts not far above a normal room temperature.
Their melting points decrease as you go down the group Li These are very reactive metals and have to be stored out of contact with air. This page introduces the Alkali Metals in Group 1 of the Periodic Table.įrancium is so radioactive and short-lived that nobody has ever seen a lump of it! We can, however, predict what its properties might be by exploring the trends in the group.
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