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

What is the electronic configuration of argon?

1. 2.8

2. 2.8.8.1

3. 2.8.8

4. 2.8.7

The correct answer is: 2.8.8

The electronic configuration of argon is represented as 2.8.8. This indicates that argon, which has an atomic number of 18, has a total of 18 electrons. These electrons are arranged in energy levels or shells around the nucleus. The first shell can hold a maximum of 2 electrons, which is satisfied, hence the notation "2." The second shell can hold up to 8 electrons, and in argon, it is also fully filled, represented by the "8." The third shell can accommodate up to 18 electrons, but in argon, it contains another complete set of 8 electrons as well. Therefore, the configuration 2.8.8 accurately reflects that argon has filled outer shells, making it one of the noble gases characterized by high stability and low reactivity. This setting is significant because it explains argon's chemical inertness. The other configurations mentioned do not represent argon accurately. For example, "2.8" does not account for all the electrons in argon, and "2.8.8.1" inaccurately suggests an additional electron which belongs in a next shell not occupied in a neutral argon atom. "2.8.7" also mis