International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

How does the reactivity of astatine compare to that of iodine?

1. Astatine is more reactive

2. Astatine is equally reactive

3. Astatine is less reactive

4. Astatine is not reactive

The correct answer is: Astatine is less reactive

Astatine is indeed less reactive than iodine, which is an important aspect given the properties of halogens. Reactivity in halogens, such as iodine and astatine, generally decreases as you move down the group in the periodic table. This trend occurs because, as the atomic number increases, the number of electron shells also increases, resulting in a greater distance between the outermost electrons and the nucleus. This increased distance weakens the nuclear attraction on the outer electrons, making it more difficult for these atoms to gain an additional electron needed for reactivity. In the case of iodine, it is relatively reactive among the halogens due to its ability to attract and gain electrons. Astatine, being lower in the group, has its outer electrons further from the nucleus, resulting in a decrease in reactivity compared to iodine. Consequently, astatine's behavior as a less reactive element reflects the atomic structure and periodic trends within the group of halogens. Understanding these trends is essential for predicting the properties of elements based on their position in the periodic table.