Chapter U1.14, Problem 1TAI

Interpretation Introduction

Interpretation:

Different types of isotopes of elements have to be explained.

Concept introduction:

Atoms with same number of protons but different number of neutrons are called isotopes. An element may have one or more isotopes. Some isotopes are very stable and some are unstable.

Answer to Problem 1TAI

Elements have two types of isotopes. These are:

• Naturally occurring isotopes
• Radioactive isotopes

Explanation of Solution

Given information: There are many types of isotopes of elements.

Naturally occurring isotopes - Some elements have very stable isotopes. These are found naturally on Earth. There are about 92 naturally occurring elements on the periodic table. Other elements exist as a result of human activity or strange circumstances. These isotopes have stable nuclei as there is a balance between the number of protons and number of neutrons in the nuclei. Examples: Beryllium has only one naturally occurring isotope; ${}_4^9\text{Be}$

Helium has two naturally occurring isotopes: ${}_2^4{\text{He and }}_2^3\text{He}$

Radioactive isotopes - These are highly unstable isotopes. They have either very few neutrons or too many neutrons. They emit small parts of their nuclei. Such atoms undergo radioactive decay; that is they decay over time as particles are continuously emitted from the nucleus. All elements beyond atomic number 83 are unstable.

Examples: Hydrogen, argon, cerium, have radioactive isotopes. Majority of radioactive isotopes are elements with atomic numbers above 83. Elements beyond polonium such as technetium, promethium, etc have only radioactive isotopes.

Conclusion

Most of the naturally occurring isotopes are stable. They have the right balance of protons and neutrons. Unstable isotopes are known as radioactive isotopes. Elements beyond atomic number 83 have radioactive isotopes.