which among them are the heavy ones?
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is lithium a metal? Yes,  a soft, silvery-white alkali metal. what is meant by this last term? The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). Together with hydrogen they constitute group 1 how is it connected to our solar system? All the alkali metals have odd atomic numbers and they are not as common as the elements with even atomic numbers adjacent to them (the noble gases and the alkaline earth metals) in the Solar System. where it is applied? Lithium is often used in lithium-ion batteries, and lithium oxide can help process silica. Sodium compounds have many applications, the most well-known being sodium chloride as table salt. Potassium compounds are often used as fertilisers
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Alkali metal [SEP] Applications
Lithium, sodium, and potassium have many applications, while rubidium and caesium are very useful in academic contexts but do not have many applications yet. Lithium is often used in lithium-ion batteries, and lithium oxide can help process silica. Lithium stearate is a thickener and can be used to make lubricating greases; it is produced from lithium hydroxide, which is also used to absorb carbon dioxide in space capsules and submarines. Lithium chloride is used as a brazing alloy for aluminium parts. Metallic lithium is used in alloys with magnesium and aluminium to give very tough and light alloys. Sodium compounds have many applications, the most well-known being sodium chloride as table salt.