Noble gases are a unique group of elements known for their stability and minimal reactivity due to their full outer electron shells. This characteristic is achieved by having a specific number of valence electrons. Among the noble gases, the most common configuration is to have 8 valence electrons, except for helium, which has only 2. However, there is another group of noble gases known as the “inert pair effect elements” which have only 2 valence electrons instead of 8.
Despite the general trend of noble gases having 8 valence electrons, there are exceptions to this rule. The inert pair effect elements, such as thallium and lead, exhibit a tendency to retain their outermost s electrons instead of participating in chemical bonding. This unique behavior results in these noble gases having only 2 valence electrons, rather than the typical 8 found in other members of the group.
What are noble gases?
Noble gases are a group of chemical elements that are located on the far right side of the periodic table. These elements include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Noble gases are known for their low reactivity and stability due to the presence of a full outer electron shell, which makes them extremely unreactive under normal conditions.
What are valence electrons?
Valence electrons are the electrons present in the outermost energy level of an atom. They are responsible for the chemical properties and reactivity of an element. The number of valence electrons in an atom determines its ability to form bonds and participate in chemical reactions.
The valence electron configuration of noble gases
Each noble gas has a unique electron configuration, which determines the number of valence electrons it possesses.
Helium (He)
Helium is the first noble gas located in the periodic table. It has an atomic number of 2, indicating that it has two electrons. Since the first energy level can hold a maximum of 2 electrons, helium has a full outer electron shell with a configuration of 2.
Neon (Ne)
Neon is the second noble gas. It has an atomic number of 10 and a total of 10 electrons. The electron configuration of neon is 2-8, indicating that it has 8 electrons in its second energy level, which is its valence shell.
Argon (Ar)
Argon is the third noble gas. It has an atomic number of 18 and an electron configuration of 2-8-8. This means that argon has 8 valence electrons located in its third energy level.
Krypton (Kr)
Krypton is the fourth noble gas. It has an atomic number of 36 and an electron configuration of 2-8-18-8. This implies that krypton has 8 valence electrons located in its fourth energy level.
Xenon (Xe)
Xenon is the fifth noble gas. It has an atomic number of 54 and an electron configuration of 2-8-18-18-8. This means that xenon has 8 valence electrons, which are situated in its fifth energy level.
Radon (Rn)
Radon is the sixth and last noble gas. It has an atomic number of 86 and an electron configuration of 2-8-18-32-18-8. Radon, like other noble gases, has 8 valence electrons in its outermost energy level.
Do all noble gases have 7 valence electrons?
No, not all noble gases have 7 valence electrons. In fact, none of the noble gases have exactly 7 valence electrons. The number of valence electrons in noble gases depends on their position in the periodic table.
Helium, as mentioned earlier, has only 2 valence electrons, not 7. Neon, argon, krypton, xenon, and radon all have 8 valence electrons in their outermost energy level, except for helium.
It’s important to note that the octet rule, which states that atoms tend to gain, lose, or share electrons to acquire a complete set of 8 valence electrons, applies to most elements but not noble gases. This is because noble gases already have a full outer electron shell, making them stable and unreactive.
While noble gases are generally unreactive, they can form compounds under certain conditions. However, these compounds are highly unstable and require extreme conditions to form. Despite this, noble gases are still commonly referred to as “inert gases” due to their low reactivity.
Noble gases, with the exception of helium, have 8 valence electrons in their outermost energy level. These elements are known for their low reactivity and stability due to the presence of a full outer electron shell. Understanding the valence electron configuration of noble gases helps explain their unique properties and their minimal tendency to form chemical compounds.
Not all noble gases have 7 valence electrons. While the majority of noble gases do have 8 valence electrons, Helium is an exception with only 2 valence electrons.argon, krypton, and xenon all have 8 valence electrons, giving them full outer shells.