Chapter 12, Problem 1ALQ

sing only the periodic table, predict the most stable ion for $\text{Na},\text{ Mg},\text{ Al},\text{ s},\text{ Cl},\text{ K},\text{ Ca},\text{ and Ga}$. Arrange these elements from largest to smallest radius and explain why the radius varies as it does.

Interpretation Introduction

Interpretation:

The most stable ions of $\text{Na,}\text{Mg,}\text{Al,}\text{S,}\text{Cl,}\text{K,}\text{Ca,}$ and $\text{Ga}$ are to be predicted. The given elements are to be arranged in order of decreasing radii and the reason as to why the radius varies is to be stated.

Concept Introduction:

The gain or loss of electrons from an atom results in the formation of ionic species. The atoms bearing positive and negative charges combine to form an ionic compound. The radii of ions are different as compared to their parent atoms because ions either possess negative charge or positive charge on them.

Answer to Problem 1ALQ

The most stable ions for $\text{Na,}\text{Mg,}\text{Al,}\text{S,}\text{Cl,}\text{K,}\text{Ca,}$ and $\text{Ga}$ are $\text{N}{\text{a}}^{+},{\text{Mg}}^{2+},{\text{Al}}^{3+},{\text{S}}^{2-},{\text{Cl}}^{-},{\text{K}}^{+},{\text{Ca}}^{2+}$ and ${\text{Ga}}^{3+}$ respectively. The arrangement of elements in order of decreasing radii on the basis of position of elements in the periodic table is shown below.

$\text{K}>\text{Ca}>\text{Na}>\text{Mg}>\text{Ga}>\text{Al}>\text{S}>\text{Cl}$

The atomic radii increase down the group due to increase in the number of shells, whereas it decreases along the period from left to right due to the addition of electrons in the same valence shell.

Explanation of Solution

The ions become stable when they acquire complete octet. The positive and negative value of ion denotes the number of electrons gained or lost. Therefore, the most stable ions for $\text{Na,}\text{Mg,}\text{Al,}\text{S,}\text{Cl,}\text{K,}\text{Ca,}$ and $\text{Ga}$ are $\text{N}{\text{a}}^{+},{\text{Mg}}^{2+},{\text{Al}}^{3+},{\text{S}}^{2-},{\text{Cl}}^{-},{\text{K}}^{+},{\text{Ca}}^{2+}$ and ${\text{Ga}}^{3+}$ respectively.

The positively and negatively charged atom is referred to as a cation and an anion respectively.

The arrangement of elements in order of decreasing radii on the basis of position of elements in the periodic table is shown below.

$\text{K}>\text{Ca}>\text{Na}>\text{Mg}>\text{Ga}>\text{Al}>\text{S}>\text{Cl}$

The atomic radii increase down the group due to increase in the number of shells, whereas it decreases along the period from left to right due to the addition of electrons in the same valence shell.

Conclusion

The most stable ions for $\text{Na,}\text{Mg,}\text{Al,}\text{S,}\text{Cl,}\text{K,}\text{Ca,}$ and $\text{Ga}$ are $\text{N}{\text{a}}^{+},{\text{Mg}}^{2+},{\text{Al}}^{3+},{\text{S}}^{2-},{\text{Cl}}^{-},{\text{K}}^{+},{\text{Ca}}^{2+}$ and ${\text{Ga}}^{3+}$ respectively. The arrangement of elements in order of decreasing radii on the basis of the position of elements in the periodic table is shown below.

$\text{K}>\text{Ca}>\text{Na}>\text{Mg}>\text{Ga}>\text{Al}>\text{S}>\text{Cl}$

The atomic radii increase down the group due to increase in the number of shells, whereas it decreases along the period from left to right due to the addition of electrons in the same valence shell.