Boron does not form `B^(3+)` ion. Why?

(i) Carbon atom does not form C^(4-) anion and C^(4+) cation. Why ? (ii) How can ethanol be converted into ethanoic acid?

Though nitrogen exhibit +5 oxidiation state, it does not form pentahalide. Why?

Why hard water does not form lather with soap ? What advantage has soap over detergents ?

NH_(3) does not form complex with