Question

Why do 1 iron and 2 oxygen make Fe2O3?

Answer 1

Answer on Question #53269 – Chemistry – Other

Question:

Why do 1 iron and 2 oxygen make $\mathrm{Fe_2O_3}$?

Answer:

It happens because the Iron and the oxygen atoms have the valences of 3 and 2, respectively. It comes from their electronic configurations: [Ar] $3\mathrm{d}^6$ $4\mathrm{s}^2$ for Iron and [He] $2\mathrm{s}^2$ $2\mathrm{p}^4$. Iron atom gives 3 electrons to form the most stable configuration [Ar] $3\mathrm{d}^5$, and oxygen atom takes 2 electrons to complete its sub-level containing 8 electrons: [He] $2\mathrm{s}^2$ $2\mathrm{p}^6$.

Since we can't break atom into the parts, namely to write $\mathrm{Fe_{1/3}O_{1/2}}$, we should find the common denominator for these coefficients (1/3 and 1/2). It is clear that the denominator equals 6. Thus, if we divide the denominator into the valences of atoms we find, for iron, $6/3 = 2$ and for oxygen $6/2 = 3$. Finally the right formula should be $\mathrm{Fe_2O_3}$.

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