Chapter 11, Problem 57A

(a)

Interpretation Introduction

Interpretation:Atomic size of thegiven set of elements $\left(\text{S,Al,Ar,Na}\right)$ must be provided.

Concept introduction:Arrangement of all existing elements in the order of their atomic numbers leads to formation of periodic table. There are total of 18 vertical groups or columns and 7 periods or rows in the periodic table. This arrangement of elements explains a lot of their properties such as atomic size.

Atomic size is the distance in $\stackrel{0}{\text{A}}$ unit starting from the centre of nucleus to the outer most valence shell.

Answer to Problem 57A

Correct order of atomic size for the elements in increasing order is $\text{Na}>\text{Ar}>\text{Al}>\text{S}$ .

Explanation of Solution

On moving horizontally from group 1 to group 18 in periodic table, atomic size of elements trends in decreasing order. Reason for this trend is that with increase in atomic number(Z), number of electron that enter into same shell keeps on increasing. In addition to it, there is an increase in nuclear charge too which pull the valence electrons closer to it. Hence atomic size decreases.

On moving below from row 1 to row 7, atomic size show increasing trend due to addition of 1 new shell with each new row. Hence the nuclear pull decreases on valence shell and atomic size increases.

  $\text{S}$ belongs to group 16, $\text{Al}$ to group 13,Na to group 1and Ar to group 18,therefore the atomic size trend seen among them is: $\text{Na}>\text{Ar}>\text{Al}>\text{S}$ . Ar has larger atomic size than Al and S is due to its inert configuration.

(b)

Interpretation Introduction

Interpretation: Atomic size of the given set of elements $\left(\text{K,Li,Rb,Cs}\right)$ must be provided.

Concept introduction: Arrangement of all existing elements in the order of their atomic numbers leads to formation of periodic table. There are total of 18 vertical groups or columns and 7 periods or rows in the periodic table. This arrangement of elements explains a lot of their properties such as atomic size.

Atomic size is the distance in $\stackrel{0}{\text{A}}$ unit starting from the centre of nucleus to the outer most valence shell.

Answer to Problem 57A

Correct order of atomic size for the elements in increasing order is $\text{Cs}>\text{Rb}>\text{K}>\text{Li}$ .

Explanation of Solution

On moving horizontally from group 1 to group 18 in periodic table, atomic size of elements trends in decreasing order. Reason for this trend is that with increase in atomic number, number of electron that keeps on increasing, enter into same shell. Whereas there is an increase in nuclear charge too which pull the valence electrons closer to it. Hence atomic size decreases.

On moving below from row 1 to row 7, atomic size show increasing trend due to addition of 1 new shell with each new shell. Hence the nuclear pull decreases on valence shell and atomic size increases.

  $\text{Cs}$ , $\text{Rb}$ , $\text{Li \& K}$ belongs to group1therefore theatomic size trend seen among them is: $\text{Cs}>\text{Rb}>\text{K}>\text{Li}$ due to new added shell and decrease in nuclear change.

(c)

Interpretation Introduction

Interpretation: Atomic size of the given set of elements $\left(\text{Br,As,Kr,Ca}\right)$ must be provided.

Concept introduction: Arrangement of all existing elements in the order of their atomic numbers leads to formation of periodic table. There are total of 18 vertical groups or columns and 7 periods or rows in the periodic table. This arrangement of elements explains a lot of their properties such as atomic size.

Atomic size is the distance in $\stackrel{0}{\text{A}}$ unit starting from the centre of nucleus to the outer most valence shell.

Answer to Problem 57A

Correct order of atomic size for the elements in increasing order is $\text{Ca}>\text{Kr}>\text{As}=\text{Br}$ .

Explanation of Solution

On moving horizontally from group 1 to group 18 in periodic table, atomic size of elements trends in decreasing order. Reason for this trend is that with increase in atomic number, number of electron that keeps on increasing, enter into same shell. Whereas there is an increase in nuclear charge too which pull the valence electrons closer to it. Hence atomic size decreases.

On moving below from row 1 to row 7, atomic size show increasing trend due to addition of 1 new shell with each new shell. Hence the nuclear pull decreases on valence shell and atomic size increases.

  $\text{Ca}$ belongs to group 2, $\text{As}$ to group 15, Br to group 17and Kr to group 18,therefore theatomic size trend seen among them is: $\text{Ca}>\text{Kr}>\text{As}=\text{Br}$ . Same size of Br and As is due to poor shielding effect of $3d^{10}$ electrons.