I want to know elements of the periodic table which are strictly cations and anions, unlike H, C, Si, Ge, As, Sb, At,etc which can be both (i.e. amphoteric elements). Also, kindly add to this list of amphoteric elements if I have missed any.
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There are no elements that only form one type of ion. In your words, there are no elements that "strictly" form only one type of ion. However, by comparing their ionization energies and electron affinities, we can say these elements are more likely to form cations or anions. For example, alkali metals have very low ionization energies and low electron affinities, which means they are more likely to form cations. Conversely, halogens have very high ionization energies and very high electron affinities, which means that they can easily form anions. But if we bombard a sodium atom with a high-energy electron, this electron will be absorbed by the sodium, turning it into an anion. Even though it is a very short-lived anion, it is still converted into an anion.
Therefore, you cannot "strictly" specify an element to only form a specific ion. You can only say these elements are more likely to form a particular type of ion. Metals usually form cations. Non-metals usually form anions. Metalloids can form both types of ions.
I hope this answers your question. If there is anything else, I would be happy to reply.
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$\begingroup$ Thanks@Sameer. I now understand that under extreme conditions elements can switch between cations to anions. But in normal conditions and long-lived states, can all metals / non-metals / metalloids be cations / anions / both? $\endgroup$– AbPhysCommented Jul 26 at 11:39
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