Chapter U1.19, Problem 15E

Interpretation Introduction

Interpretation:

The ion with the correct charge needs to be identified.

Concept introduction:

The charge of an ion depends on the number of valence electrons present in it. If the number of valence electrons is less than or equal to 3, atoms prefer to lose electron/s to get a positive charge and if the number of valence electrons is more than or equal to 5 they prefer to get a negative charge.

Answer to Problem 15E

  ${\text{Li}}^{+}$ , ${\text{Ca}}^{2+}$ and ${\text{Ga}}^{3+}$ have correct charges.

Explanation of Solution

Lithium is an alkali metal thus contain one valence electron. So, it will produce mono positive cation ( ${\text{Li}}^{+}$ ).

Calcium is an alkaline earth metal thus contain two valence electrons and so it will produce dipositive ion ( ${\text{Ca}}^{2+}$ ).

Galium is a p block element thus, contain three valence electrons similar to aluminum. So, it will produce tripositive ion( ${\text{Ga}}^{3+}$ ).

Conclusion

The charge on the Na atom cannot be +2 because it belongs to group 1, that is, alkali metal. It can lose 1 electron thus, the correct charge on Na ion is +1.

Similarly, the charge on the Al atom cannot be +4 because it belongs to group 13. It can lose 3 electrons to form a stable ion with a stable electronic configuration.