Chapter 7, Problem 129A

Interpretation Introduction

(a)

Interpretation:

The symbol and name of the second-lightest element of the halogen needs to be determined.

Concept introduction:

The halogens are placed on the left of the noble gases on the periodic table. They are comprises of total of 5 elements.

Answer to Problem 129A

Chlorine is the second-lightest element of the halogen and its symbol is $\text{Cl}$.

Explanation of Solution

In the periodic table, group 17 elements are known as halogens which include fluorine, chlorine, bromine, iodine and astatine. Atomic masses of halogens increases down the group. Therefore, fluorine is the first-lightest element among them. Hence, it is clear that chlorine is the second-lightest element in this group.

(b)

Interpretation Introduction

Interpretation:

The symbol and name of the metalloid of lowest period number needs to be determined.

Concept introduction:

Metalloid shows the intermediate properties between metal and non-metals. Total of eight metalloids is found in the periodic table.

Answer to Problem 129A

Boron is the metalloid which has lowest period number its symbol is $\text{B}$.

Explanation of Solution

Metalloids are placed right between metals and non metals. They consist of boron, silicon, germanium, arsenic, antimony, tellurium, polonium and astatine. The periods are numbered from 1 which is top row to 7 which is bottom row on the periodic table. Metalloid boron is placed at the second period. Therefore, it has the lowest period number.

(c)

Interpretation Introduction

Interpretation:

The symbol and name of the group 16 element this is gas at room temperature needs to be determined.

Concept introduction:

Group 16 elements are known as oxygen family. They are comprises of total of five elements.

Answer to Problem 129A

Group 16 element oxygen is gas at room temperature and its symbol is $\text{O}$.

Explanation of Solution

The group 16 elements consist of oxygen, sulfur, selenium, tellurium, and polonium. Generally, they are solids or liquids at room temperature. Among these elements oxygen is gas at room temperature.

(d)

Interpretation Introduction

Interpretation:

The symbol and name of the heaviest noble gas needs to be determined.

Concept introduction:

Group 18 elements are known as noble gas. This group is comprises of total of six elements. They are chemically inactive because they have completely filled valence electron shell.

Answer to Problem 129A

Radon is the heaviest noble gas and its symbol is $\text{Rn}$.

Explanation of Solution

Group 18 elements are known as noble gas. This group comprises a total of six elements. They are helium, neon, argon, krypton, xenon, and radon. The mass of atoms increases top to bottom in a group. Therefore, among them mass of radon is highest. Hence, it is the heaviest noble gas.

(e)

Interpretation Introduction

Interpretation:

The symbol and name of the group 15 element that is solid at room temperature needs to be determined.

Concept introduction:

Group 15 elements are known as nitrogen family. They are comprises of total of five elements nitrogen, phosphorus, arsenic, antimony and bismuth. They have completely filled s-orbital and half filled or completely filled p-orbital.

Answer to Problem 129A

Group 15 element Nitrogen is gas at

room temperature and its symbol is $\text{N}$.

Explanation of Solution

Group 15 elements are comprises of metal, non-metals and metalloids. The non-metals which are placed in group 15 are nitrogen and phosphorus. From these two elements nitrogen is gas at room temperature.