Q.5.4 - An Introduction to General, Organic, and Biological Chemistry

Question

Naturally occurring iodine is iodine-127. Medically, radioactive isotopes of iodine-125 and iodine-131 are used. 

a. Write the atomic symbol for each isotope. 

b. In what ways are the isotopes similar, and in what ways do they differ?

Step-by-Step Solution

Answer

a. The atomic symbol for each isotope is: ${}_{53}{}^{127}\mathrm{I} \mathrm{and} {}_{53}{}^{131}\mathrm{I}$.

b. All the isotopes have same number of protons and electrons but differ in the number of neutrons. 

Step 1: Part (a) Given Information

We need to mention isotopic forms of Iodine.

Step 2: Part (a) Explanation

In atomic symbols, the mass number is written in the upper left corner while the atomic number is written in the lower-left corner. The addition of the number of protons and neutrons in the nucleus is defined as the mass number, while the atomic number is the total number of protons.  

The atomic symbol for each isotope of Iodine can be represented as: 

$$\begin{gathered} \mathrm{Iodine}-127\to {}_{53}{}^{127}\mathrm{I} \\ \mathrm{Iodine}-125\to {}_{53}{}^{125}\mathrm{I} \\ \mathrm{Idoine}-131\to {}_{53}{}^{131}\mathrm{I} \end{gathered}$$

Step 1: Part (a) Given Information

We need to mention the ways in which these isotopes are similar and different. 

Step 2: Part (b) Explanation

The atomic symbol for each isotope of Iodine can be represented as: 

$$\begin{gathered} \mathrm{Iodine}-127\to {}_{53}{}^{127}\mathrm{I} \\ \mathrm{Iodine}-125\to {}_{53}{}^{125}\mathrm{I} \\ \mathrm{Idoine}-131\to {}_{53}{}^{131}\mathrm{I} \end{gathered}$$

While looking at each isotope, we observe that the atomic number remains the same or the number of protons and number of electrons is the same. And if we look at the mass number it keeps on changing for different isotopes which means the number of neutrons is different.