Question

Which element has the highest boiling point?
A. He
B. Ne
C. Kr
D. Xe

Answer 1

Hint: The answer has various applications in incandescent lighting, X-ray development; plasma display panels (PDPs). To know the answer of this question, we should follow the trend in boiling point of noble gases.

Step by step answer:
As we know that all the options are from the noble gas group. And these can be arranged as follows:

Element	Atomic Number
Helium	2
Neon	10
Krypton	36
Xenon	54

From the table we can say that the atomic number is increasing. As we go down the group atomic mass and atomic radii increases. Because the atoms increase in atomic size down the group, the electron clouds of these non-polar atoms become increasingly polarized, which leads to weak van Der Waals forces among the atoms. The boiling points of noble gases are very low in comparison to those of other substances of comparable atomic and molecular masses. Thus, the formation of liquids and solids is more easily attainable for these heavier elements because of their melting and boiling points.
The van der Waals force increases with the increase in the size of the atom, and therefore, in general, the boiling point increases from Helium to Radon. Xenon has larger mass than helium and has larger dispersion forces. Because of larger size the outer electrons are less tightly held in the larger atoms so that instantaneous dipoles are more easily induced resulting in greater interaction between argon atoms. Therefore, its boiling point (-108.1 °C) is more than that of Helium.
From the concept we can say that from option A to option D, our atomic number as well as atomic mass is increasing so van der Waals forces are also increasing. This leads us to the answer.
So, Xenon has the highest atomic number among these, so according to the above points we can say that our correct option is D.

Notes:

Noble gases	Boiling point (C)	Atomic weight
Helium	-268.93	4.008
Neon	-246.08	20.18
Krypton	-153.22	83.8
Xenon	-108.00	131.93

We should know that the noble gases are colourless, odourless, tasteless, non-flammable gases. We know them by the label Group “0” in the periodic table because for decades after their discovery it was believed that they could not bond to other atoms; that is, that their atoms could not combine with those of other elements to form chemical compounds. When the members of the group were discovered and identified, they were thought to be exceedingly rare, as well as chemically inert, and therefore were called the rare or inert gases. It is interesting to note that several of these elements are quite abundant on Earth and in the rest of the universe, so the designation rare is misleading.