Which group of elements have a full octet of electrons? Click ‘View Image’ to look at the periodic table. a) Noble gases b) Halogens c) Alkali metals d) Transition metals
The Correct Answer and Explanation is:
Correct Answer: a) Noble gases
Explanation
The noble gases are the group of elements that naturally have a full octet of electrons in their outermost electron shell (valence shell), which makes them uniquely stable and unreactive compared to other elements. Located in Group 18 (or Group 8A in older notations) of the periodic table, noble gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).
For elements like neon, argon, and xenon, the full octet refers to having eight electrons in their valence shell. This configuration is highly stable because it completes the outer s and p orbitals, minimizing the atom’s tendency to gain or lose electrons in chemical reactions. Helium is an exception in terms of electron count—it has only two electrons, but this completely fills its first energy level (1s²), making it stable as well, even though it doesn’t follow the “octet” rule numerically.
In contrast:
- Halogens (Group 17) have seven valence electrons and need one more to complete their octet. This makes them highly reactive as they tend to gain an electron during chemical reactions.
- Alkali metals (Group 1) have one valence electron and are also highly reactive, but in the opposite way—they tend to lose one electron to achieve a noble gas configuration.
- Transition metals (Groups 3–12) have more complex electron configurations and do not consistently follow the octet rule. They often use d-orbitals in bonding and may have incomplete octets.
In summary, noble gases are the only group on the periodic table that naturally possess a full outer shell of electrons, giving them chemical inertness and setting them apart from other groups.
