Chapter 3, Problem 9STP

Interpretation Introduction

Interpretation: The correct letter in the space needs to be determined.

Concept introduction:  A table in chemistry, where all elements are arranged by increasing atomic number is described as periodic table. There are more than 100 elements in the world and the periodic table classifies these elements.

Answer to Problem 9STP

The correct letter in the space provided:

1. Alkaline earth metals
2. Halogens
3. Alkali metals
4. Noble Gases

Explanation of Solution

The periodic table is a very useful way to arrange elements. In a periodic table, the border line between the metals and non-metals are defined as “stair-step” line. Elements that are on the right side of stairs, called non-metals and elements that are on right side of stairs, called metals.  Elements along the stair-step line are known as metalloids. In the periodic table vertical columns are known as families.

The alkaline earth metals are the second most active metals in the periodic table. Elements from these group are also known as Group $2$ elements. They have a full s orbital. The correct letter, a, in the space provided is alkaline earth metals.

Halogen means salt-former and compound containing halogens are called “salts”. It exists in all three states of matter. This element is very reactive. The correct letter, b, in the space provided is Halogen.

In a periodic table, elements of Group $1$ are known as Alkali metals. Reactivity of this group increases as you go down the family. It has low density and low melting point. The correct letter, c, in the space provided is Alkali metals.

In a periodic table, elements of Group $18$ are known as noble gas. The noble gases don’t react with anything. They are neither metalloid nor a metal. Noble gases are also called ‘inert gas’. They are colorless and odorless. They have a full outer electron shell, which makes these elements non-reactive. The correct letter, d, in the space provided is noble gas.

Conclusion

In a periodic table, elements are divided according to their chemical behaviour.