Which of the following statements is true? a. noble gases are very reactive. b. noble gases are each a different color. c. halogens are inert. d. noble gases are found as monatomic molecules.

The correct options is:

D. Noble gases are found as monatomic molecules.

Explanation:

The noble gases are a group of elements of the periodic table that are characterized, in normal conditions of pressure and temperature, for being monoatomic gases without odor, without color and with very low chemical reactivity.

The noble gases encompass the elements of group 18 of the periodic table and include six elements: Helium, Neon, Argon, Krypton, Xenon and Radon.

Valencia electrons are the electrons found in the last electronic layer (called valence orbitals). These electrons are what determine the ability of the atom to form bonds.  The noble gases do not combine with other atoms because they are very stable because they have the full valence layer that gives them a low tendency to capture or release electrons. That is why they are also called inert gases.

Halogens are five non-metallic elements that are located in group 17 of the periodic table.

Taking into account everything mentioned above, the correct option is:

D. Noble gases are found as monatomic molecules.