Chapter 17, Problem 69A

To determine

To Explain: The importance of periodic table of elements

The difference between atoms, elements and molecules.

Explanation of Solution

Introduction:

Regular arrangement of elements in a tabular form is called periodic table of elements.

There are so many elements present in the nature. Some are artificial or manmade. Some are radioactive in nature. It was very difficult to remember the names and properties of all the elements. So, Mendeleev formulated this idea of putting all the elements in the table in a periodic way, called periodic table of elements. Study of elements becomes very easy after this type of arrangements of elements.

Atoms:

Atoms are the smallest of matter. It consists of nuclear and extra-nuclear part. Nuclear part consists of positively charged protons and neutrons. Extra-nuclear part is the part outside the nucleus which consists of negatively charged electrons revolving in affixed orbits/shells.

Element:

Element consists of same types of atoms.

Molecules:

A molecule consists of two or more atoms. There are two types of molecules; homoatomic and heteroatomic molecules.

In homoatomic-molecules, both the atoms are same. For example, in ${\text{H}}_{\text{2}}$ molecule both the atoms are same i.e. Hydrogen.

In heteroatomic molecules, both the atoms are different. For example, in ${\text{CO}}_{\text{2}}$ molecule one element of Carbon and two elements of Oxygen is involved.

Conclusion:

Periodic table of element is very useful for understanding the properties of elements.