Which of the following is NOT a noble gas?
a) Helium b) Neon c) Argon d) Hydrogen
The Correct Answer and Explanation is:
The correct answer is d) Hydrogen.
Explanation:
Noble gases are a group of chemical elements that are characterized by their stable electron configurations. They are located in Group 18 of the periodic table and include the following elements: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). These gases are known for their lack of reactivity because they have a full outer electron shell, which makes them chemically stable and unlikely to form bonds with other elements.
Now, let’s examine each of the options:
- a) Helium (He): Helium is a noble gas. It has an atomic number of 2, and its electron configuration is 1s², meaning it has a full outer shell of two electrons. This makes helium chemically stable and nonreactive, fitting the criteria for a noble gas.
- b) Neon (Ne): Neon is another noble gas. It has an atomic number of 10, and its electron configuration is 1s² 2s² 2p⁶, which means its outermost shell contains 8 electrons, making it chemically inert and stable.
- c) Argon (Ar): Argon is also a noble gas. With an atomic number of 18, argon’s electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶, and like helium and neon, it has a full outer electron shell, making it stable and unreactive.
- d) Hydrogen (H): Hydrogen is not a noble gas. It is the simplest element with only one proton and one electron. Its electron configuration is 1s¹, which means it only has one electron in its outer shell, making it chemically reactive. Unlike noble gases, hydrogen often forms bonds with other elements to fill its outer shell, as seen in compounds like water (H₂O) and hydrogen chloride (HCl).
In conclusion, while helium, neon, and argon are noble gases with stable, full electron configurations, hydrogen is not a noble gas due to its reactive nature and incomplete electron shell.