Identify the cations and anions present in aluminium oxide :

Options

A. `{:("Cation","Anion"),(Al^+, O^(-)):}`
B. `{:("Cation","Anion"),(Al^(2+), O^(2-)):}`
C. `{:("Cation","Anion"),(Al^(3+), O^(2-)):}`
D. `{:("Cation","Anion"),(Al^(3+), O^(-)):}`

Answer

C

Explanation

Aluminium oxide or `Al_2O_3` is formed by the transfer of electrons from aluminium atoms to oxygen atoms. Aluminium (Atomic number = 13) has 3 valence electrons whereas oxygen (atomic number=8) has 2 valence electrons.
So, each aluminium atom donates its 3 valence electrons to the oxygen atoms and forms cations `[Al^(3+)]`, whereas each oxygen atom gains two electrons and forms anions `[O^(2-)]`