Answer:
Halogens always form anions, alkali metals and alkaline earth metals always form cations. Most other metals form cations (e.g. iron, silver, nickel), whilst most other nonmetals typically form anions (e.g. oxygen, carbon, sulfur).
Explanation:
Examples: Sodium (Na+), Iron (Fe2+), Ammonium (NH4
Lithium, Sodium, Beryllium, and Aluminum elements form cations.
Cations means positively charged ions. Element which forms cation is Metal. Cations formed at cathode.
Anions means negatively charged ions. Element which form anions is Non metal. Anions formed at anode.
Now check one by one which elements will form cations:
(a) Lithium form cation [tex](Li^{+})[/tex], because lithium loses its electron and it form positive charge.
(b) Sodium form cation [tex](Na^{+})[/tex], since sodium is a alkali metal and sodium has tendency to lose an electron.
(c) Beryllium form cation [tex](Be^{2+})[/tex], because it donates or loses two electrons to become stable.
(d) Aluminum form cation [tex](Al^{3+})[/tex], because it loses its three electrons and has a three positive charge.
(e) Phosphorus form anion [tex](P^{3-})[/tex] , since phosphorus is a non-metal.
(f) Oxygen atom exists as neutral it neither form cation nor anion.
(g) Fluorine form anion [tex](F^{-})[/tex], because fluorine atom gains an electron.
Thus, from above conclusion we can say that Lithium, Sodium, Beryllium, and Aluminum elements form cations.
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