Chapter U1.20, Problem 7E

Interpretation Introduction

Interpretation:

The reason due to which the given compounds cannot be formed needs to be explained.

Concept introduction:

A compound must be neutral that is the total positive charge of the cations should be counterbalanced by the total anionic charge in a compound.

Answer to Problem 7E

${\text{NaCl}}_{\text{2}}$, CaCl and AlO do not form as the compounds are not neutral and violated the valency rule..

Explanation of Solution

Sodium is monovalent and chlorine is also monovalent. Thus, one sodium ion will combine with one chloride ion producing NaCl which is charge neutral. In ${\text{NaCl}}_{\text{2}}$, if the neutral ion is considered the charge on Na will be + 2 which is not possible as it has only 1 electron in its outermost shell. If the correct charge on Na and Cl is considered, the compound will have -1 charge or it will not be neutral.

Similarly, calcium has two valencies and chlorine has 1 valency. Thus one calcium ion will need two chloride ions to form a neutral compound. Thus, the formula should be ${\text{CaCl}}_{\text{2}}$. In CaCl, the charge on Ca is + 1 which is not stable. If the correct charge on both Ca and Cl is considered, the compound will have + 1 charge or it will not be neutral.

Now, Aluminium has valency 3 and oxygen has valency two. Thus 2 ${\text{Al}}^{3+}$ will react with 3 ${\text{O}}^{2-}$ producing ${\text{Al}}_{\text{2}}{\text{O}}_{\text{3}}$ which is neutral. But in AlO, the charge on the Al is + 2 which is not stable. If the correct charge on both Al and O is considered, then the compound will have + 1 charge and it will not be neutral.

Conclusion

Thus NaCl₂, CaCl and AlO do not form.