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Question Video: Determining the Common Oxidation State of Alkali Metals Chemistry

What is the common oxidation number of alkali metals?


Video Transcript

What is the common oxidation number of alkali metals?

Before we begin to identify the oxidation number of alkali metals, let us first discuss oxidation numbers. Oxidation numbers show the degree of oxidation of an atom in isolation or in a compound in terms of counting electrons. Oxidation numbers tell us how many electrons an element will gain or lose to form a bond or an ion. When looking at the periodic table, there are some groups of elements that have trends in terms of oxidation numbers. For example, noble gases in group 18 are considered chemically inert since their oxidation number is zero because they do not gain or lose any electrons. As the oxidation number of helium He and argon Ar is zero, atoms of these elements do not typically form bonds with atoms of other elements.

Moving across the periodic table to group 17 are the halogens such as fluorine F and chlorine Cl. These elements usually have oxidation numbers of negative one since they gain one electron. They can form compounds such as hydrochloric acid HCl, potassium iodide KI, and sodium bromide NaBr. Oxygen in group 16 has an oxidation number of negative two since it will gain two electrons and can form compounds such as Na2O, sodium oxide. Moving further to the left on the periodic table, we encounter the alkaline Earth metals in group two. This group includes beryllium Be, magnesium Mg, and calcium Ca. All of these metals have an oxidation number of positive two since they lose two electrons. They can also form compounds such as magnesium oxide MgO and calcium fluoride CaF2.

Finally, alkali metals are in group one which include elements such as lithium Li, sodium Na, and potassium K. Hydrogen H, which is also located in group one of the periodic table, is not an alkali metal though it has the same oxidation number as the rest of the elements in group one, which is positive one because they lose one electron and can form compounds such as sodium chloride NaCl, also known as table salt, or potassium bromide KBr. After reviewing the trends in the periodic table about some of the common oxidation numbers, we can conclude that the common oxidation number for alkali metals is positive one. Positive one is the correct answer choice.

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