How can I write the formula for aluminum oxide?

Jul 3, 2014

The formula for aluminum oxide is $A {l}_{2} {O}_{3}$.

Explanation:

The correct answer is $A {l}_{2} {O}_{3}$.

Let us see how we got the answer; Look at the electronic arrangement of Al and O atoms.

Al ( Z= 13) has 13 electrons with following electronic configuration. 1${s}^{2}$2${s}^{2}$2${p}^{6}$3${s}^{2}$3${p}^{1}$

It loses three electron in its 3s and 3p subshell to achieve stability and forms ion $A {l}^{3 +}$.

$A {l}^{3 +}$ = 1${s}^{2}$2${s}^{2}$2${p}^{6}$

O ( Z=8) on the other hand has eight electrons and wants to gain two electrons to achieve stable noble gas configuration.Oxygen atom on gaining two electrons forms negative oxide ion, ${O}^{2 -}$ ion.

O ( Z=7) = 1${s}^{2}$2${s}^{2}$2${p}^{4}$

${O}^{2 -}$ = 1${s}^{2}$2${s}^{2}$2${p}^{6}$

Three Oxygen atoms gains two electrons each ( total of six) from two Al atoms, each Al atom loses three electrons (total of six) to three oxygen atom , in this process each Al atom becomes $A {l}^{3 +}$ ion and Oxygen atom after gaining two electrons becomes ${O}^{2 -}$ ion.

2$A {l}^{3 +}$ and 3 ${O}^{2 -}$

or the formula is $A {l}_{2} {O}_{3}$.