Question

the atomic number of iron is 26 and shows +3 oxidation state when it combines with oxygen (valency of oxygen =2)
write the formula of compound
write the subshell electronic configuration of fe3+
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Answer 1

Answer:

Fe2O3

Explanation:

for the Valency

O has -2

so -2×3=-6

so Fe has

2x-6=0

x =+3

so Formula

Fe2O3

Answer 2

Given info : the atomic number of iron is 26 and shows +3 oxidation state when combines with oxygen ( valency of oxygen is 2 ).

To find : the formula of compound and the subshell electronic configuration of Fe³⁺

solution : oxidation state of Fe ion = +3

and oxidation state of O ion = -2 [ we know oxygen is non metal and it has tendency to lose electrons from its valence shell ]

ratio oxidation state of Fe to O = 3 : 2

so the formula ratio of Fe to O = 2 : 3

∴ the chemical formula of compound would be Fe₂O₃

now subshell electronic configuration of Fe³⁺ :

no of electrons in Fe³⁺ = atomic no - 3 =  26 - 3 = 23

now electronic configuration = 1s² , 2s² , 2p⁶ , 3s² , 3p⁶ , 4s⁰, 3d⁵ [ we remove 4s electrons because d needs 5 electrons to be stable as it becomes half filled subshell. ]