Chapter 13, Problem 84A

(a)

Interpretation Introduction

Interpretation: Between two atoms, the one with the larger atomic radius is to be identified.

Concept introduction:

The periodic table is a columnar structure that organizes different elements into groups based on how they behave. The elements in the periodic table of today are ordered according to the periodic law. The elements are organized in the modern periodic table in increasing order of their atomic number. When elements are arranged in increasing order of atomic number, periodic trends are observed in certain properties.

Answer to Problem 84A

S

Explanation of Solution

The elements O and S are present in the same group and S is present below O. A periodic trend is observed in atomic size also. Atomic size increases down the group. This is because when moving from top to bottom in the group, both the number of shells and nuclear charge increase. The effect of more shells, however, outweighs the effect of a higher nuclear charge which increases atomic radius.

Thus, S is bigger in size than O

(b)

Interpretation Introduction

Interpretation: Between two atoms, the one with the larger atomic radius is to be identified.

Concept introduction:

The periodic table is a columnar structure that organizes different elements into groups based on how they behave. The elements in the periodic table of today are ordered according to the periodic law. The elements are organized in the modern periodic table in increasing order of their atomic number. When elements are arranged in increasing order of atomic number, periodic trends are observed in certain properties.

Answer to Problem 84A

K

Explanation of Solution

K and Br are present in the same period. Potassium (K) is present on the extreme right whereas Br is present on the extreme right.

The atomic size decreases across the period or decreases from left to right. This is because when moving left to right in the periodic table, the number of shells stays constant while the nuclear charge increases by one at each step. As nuclear charge increases, electrons in the outermost shell are drawn to it with increasing force, which causes the size of atoms to gradually shrink over time.

Thus, K is bigger in size.