Question

Which elements had complete outer shells? Give the name and symbol for each.

a. Helium
b. Neon
c. Argon

Answer 1

Noble gases such as Helium (He), Neon (Ne), and Argon (Ar) have complete outer shells with 2, 8, and 8 electrons in their outermost shells respectively, making them stable under normal conditions.

Step-by-step explanation:

The elements with complete outer shells, known as noble gases, have filled valence electron shells, making them historically assumed to be nonreactive. The noble gases in the group 18 of the periodic table include:

1. Helium (He), with an atomic number of 2, completes its outer shell with 2 electrons.
2. Neon (Ne), with an atomic number of 10, has a complete outer shell with 8 electrons (2 in the first shell and 8 in the second).
3. Argon (Ar), with an atomic number of 18, also has a complete outer shell with 8 electrons (2 in the first shell, 8 in the second, and 8 in the third).

Though originally thought inert, the nonreactivity of these noble gases has been challenged, indicating they can form compounds under certain conditions.