Chapter 21.2, Problem 3CYU

(a)

Interpretation Introduction

Interpretation: The compound or ion of a second period element, that has formula and lewis structure analogous to given formula $P{H}^{4+}$  has to be predicted.

Concept introduction: The elements belonging to the same group of periodic table have same number of electrons in their valence shell. Thus, their physical and chemical properties are also similar.

These elements can exist in similar oxidation state due to same number of valence electrons in the outermost shell. Hence, the elements of same group form compounds with same formula.

If two elements belongs to $\text{nA}$ group of periodic table, then both the elements have $\text{+n}$ as highest oxidation number. This is because the highest oxidation number is equal to the group number. So both the elements of same group  have same oxidation number and forms analogous compound of the same chemical formula. The other possible oxidation numbers apart from the highest oxidation number are as per the number of valence electrons in the outermost shell.

However, the lighter elements of the group do not expand their octet while the heavier elements can expand their octet and form compounds with different oxidation numbers. So if the elements belong to group $\text{5A}$ of periodic table then the lighter element only has oxidation number of $+3$, which is equal to number of electrons in outermost shell. But the heavier element can have both oxidation number of $+3$ and $+5$.

So, the same number of valence electrons in outermost shell of the elements in same group is responsible for the similar chemical properties of these elements. Thus they also form compounds with same formula.

(b)

Interpretation Introduction

Interpretation: The compound or ion of a second period element, that has formula and lewis structure analogous to given formula $S_2^{2-}$  has to be predicted.

Concept introduction: The elements belonging to the same group of periodic table have same number of electrons in their valence shell. Thus, their physical and chemical properties are also similar.

These elements can exist in similar oxidation state due to same number of valence electrons in the outermost shell. Hence, the elements of same group form compounds with same formula.

If two elements belongs to $\text{nA}$ group of periodic table, then both the elements have $\text{+n}$ as highest oxidation number. This is because the highest oxidation number is equal to the group number. So both the elements of same group  have same oxidation number and forms analogous compound of the same chemical formula. The other possible oxidation numbers apart from the highest oxidation number are as per the number of valence electrons in the outermost shell.

However, the lighter elements of the group do not expand their octet while the heavier elements can expand their octet and form compounds with different oxidation numbers. So if the elements belong to group $\text{5A}$ of periodic table then the lighter element only has oxidation number of $+3$, which is equal to number of electrons in outermost shell. But the heavier element can have both oxidation number of $+3$ and $+5$.

So, the same number of valence electrons in outermost shell of the elements in same group is responsible for the similar chemical properties of these elements. Thus they also form compounds with same formula.

(c)

Interpretation Introduction

Interpretation: The compound or ion of a second period element, that has formula and lewis structure analogous to given formula $P_2{H}_4$  has to be predicted.

Concept introduction: The elements belonging to the same group of periodic table have same number of electrons in their valence shell. Thus, their physical and chemical properties are also similar.

These elements can exist in similar oxidation state due to same number of valence electrons in the outermost shell. Hence, the elements of same group form compounds with same formula.

If two elements belongs to $\text{nA}$ group of periodic table, then both the elements have $\text{+n}$ as highest oxidation number. This is because the highest oxidation number is equal to the group number. So both the elements of same group  have same oxidation number and forms analogous compound of the same chemical formula. The other possible oxidation numbers apart from the highest oxidation number are as per the number of valence electrons in the outermost shell.

However, the lighter elements of the group do not expand their octet while the heavier elements can expand their octet and form compounds with different oxidation numbers. So if the elements belong to group $\text{5A}$ of periodic table then the lighter element only has oxidation number of $+3$, which is equal to number of electrons in outermost shell. But the heavier element can have both oxidation number of $+3$ and $+5$.

So, the same number of valence electrons in outermost shell of the elements in same group is responsible for the similar chemical properties of these elements. Thus they also form compounds with same formula.

(d)

Interpretation Introduction

Interpretation: The compound or ion of a second period element, that has formula and lewis structure analogous to given formula $P{F}_3$  has to be predicted.

Concept introduction: The elements belonging to the same group of periodic table have same number of electrons in their valence shell. Thus, their physical and chemical properties are also similar.

These elements can exist in similar oxidation state due to same number of valence electrons in the outermost shell. Hence, the elements of same group form compounds with same formula.

If two elements belongs to $\text{nA}$ group of periodic table, then both the elements have $\text{+n}$ as highest oxidation number. This is because the highest oxidation number is equal to the group number. So both the elements of same group  have same oxidation number and forms analogous compound of the same chemical formula. The other possible oxidation numbers apart from the highest oxidation number are as per the number of valence electrons in the outermost shell.

However, the lighter elements of the group do not expand their octet while the heavier elements can expand their octet and form compounds with different oxidation numbers. So if the elements belong to group $\text{5A}$ of periodic table then the lighter element only has oxidation number of $+3$, which is equal to number of electrons in outermost shell. But the heavier element can have both oxidation number of $+3$ and $+5$.

So, the same number of valence electrons in outermost shell of the elements in same group is responsible for the similar chemical properties of these elements. Thus they also form compounds with same formula.