Question

1. Place these compounds in order of increasing ionic character: HF, H2S, H2O, HCl, HBr

2. The ionic radius of iron in Aegirine (NaFeSi2O6) is not the same as the ionic radius of iron in Hypersthene (FeSiO3). Suggest an explanation for this.

Please explain, thank you so much!

Answer 1

1.Ionic character can be predicted by electronegativity value.More is the electronegativity difference between two atoms of the compound ,compound will be more polar hence will have more ionic character.

Among all of them the electronegativity value is in order -

F>O>Cl>Br>S

So electronegativity difference between H atom and other mentioned atoms of the compound will be in order-

HF>H2O>HCl>HBr>H2S

Hence this will be the order of Ionic character also.

2. Let's calculate the oxidation state in both .

For Aegirine- Fe has +3 oxidation state.

For hypersthene- Fe has +2 oxidation state.

Now when Fe is present in +3 oxidation state, more number of electrons are lost than when Fe is in +2 state. Hence the attractive force on the remaining electrons increases. I.e electron are attracted more by the nucleus . This result in decrease in ionic radii of Fe+3 < Fe+2