Question

Arrange the noble gases in order of increasing boiling point. Explain your reasoning.

Short answer

He, Ne, Ar, Kr, Xe, Rn (increasing boiling point order).

Step-by-step solution

Identify Noble Gases

The noble gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). These elements are found in Group 18 of the periodic table.

Understand Boiling Point Trend

The boiling points of the noble gases generally increase as you move down the group in the periodic table. This is because larger atoms have greater dispersion forces due to an increased number of electrons.

Consider Atomic Size

Larger atoms (with more protons, neutrons, and electrons) have stronger London dispersion forces, which leads to higher boiling points. Therefore, the order of boiling points is usually from the smallest atom to the largest atom.

List Noble Gases in Order of Atomic Size

Since helium has the smallest atomic size and radon has the largest, the order from smallest to largest atomic size is: He, Ne, Ar, Kr, Xe, Rn.

Arrange Noble Gases by Boiling Point

Based on atomic size and corresponding dispersion forces, arrange the noble gases in order of increasing boiling point: He, Ne, Ar, Kr, Xe, Rn.

Key concepts

Boiling Point Trends

The boiling point of a substance is the temperature at which it changes from a liquid to a gas. Noble gases like helium, neon, argon, krypton, xenon, and radon showcase a clear boiling point trend. These elements are located in Group 18 of the periodic table. Typically, as you move from top to bottom of this group, the boiling points increase. This happens because these gases are becoming heavier and their atoms larger.

The larger the atom, the more space it needs and the stronger forces between its electrons and other nearby atoms. More electrons mean stronger intermolecular forces are needed to keep them together until they finally boil and become gas. Therefore, helium, with its smaller atomic size, has the lowest boiling point, while radon, with the largest atomic size, has the highest boiling point among them.

Periodicity

Periodicity refers to the repeating pattern of chemical and physical properties of the elements as you move through the periodic table. This pattern allows us to predict properties like boiling points based on an element's position in the table, without directly measuring them.

In the case of noble gases, periodicity predicts that their boiling points increase down the group. This trend is linked closely with their increasing atomic number and atomic mass, as heavier elements tend to have stronger intermolecular attractions, influencing their transition from liquid to gas states. By knowing an element's spot in the periodic table within Group 18, we can anticipate that its boiling point will be higher than those above it, but lower than those below it.

London Dispersion Forces

London Dispersion Forces are weak intermolecular forces resulting from temporary shifts in electron density in atoms or molecules. When there is a momentary imbalance in electron cloud distribution, it induces a weak attraction between neighboring atoms.

For noble gases, these forces are crucial because they are the only type of intermolecular forces acting among the atoms. Larger noble gas atoms like xenon have more electrons. Consequently, they have stronger London Dispersion Forces compared to smaller atoms like neon. This increased force means more energy is required to separate the atoms into a gaseous state, hence a higher boiling point.

• London Dispersion Forces increase with more electrons.
• Larger atoms have stronger dispersion forces.
• Higher dispersion forces result in higher boiling points.

Understanding these forces allows us to explain why radon has a higher boiling point than helium, emphasizing the role of atomic size and electron count.