Question

An atom has 18 protons and 8 valence electrons. Which statement would best identify this element?

A. The element is highly reactive with eight electrons in its outer shell.
B. The element has an atomic mass of 18.
C. The element is happy or stable because its outer energy level is filled.
D. The element is a metal.

Answer 1

The element with 18 protons and 8 valence electrons is argon (Ar), which is a stable element in Group 18 of the periodic table.

Step-by-step explanation:

The element with 18 protons and 8 valence electrons is argon (Ar), which is located in Group 18 (Group VIII) of the periodic table, commonly known as the noble gases. In this group, the outer energy level is filled with electrons, making the element stable and less likely to react with other atoms. Therefore, the best statement to identify this element is C. The element is happy or stable because its outer energy level is filled.