Which of the following Group 18 elements is the most abundant in the Earth's atmosphere?
Helium
Neon
Argon
Krypton
Argon is the most abundant Group 18 element in the Earth's atmosphere, making up approximately 0.93% of the atmosphere by volume. Helium is the second most abundant, but it only makes up about 0.0005% of the atmosphere. Hence option C is the correct answer.
Option (A) is incorrect because helium is not the most abundant Group 18 element in the Earth's atmosphere. Hence option A is incorrect
Option (B) is incorrect because neon is not the most abundant Group 18 element in the Earth's atmosphere. Hence option B is incorrect.
Option (D) is incorrect because krypton is not the most abundant Group 18 element in the Earth's atmosphere. Hence option D is incorrect.