1.2.4 Group 1

In this lesson, we will explore the characteristics of noble gases, their stable electron arrangements, and the relationship between their boiling points and relative atomic mass.

Noble Gases

The elements in Group 0 of the periodic table are known as the noble gases. This group includes helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Noble gases are characterised by their unreactivity and reluctance to form molecules or compounds under normal conditions.

Stable Electron Arrangements

Noble gases have stable arrangements of electrons in their atoms, which contribute to their low reactivity. Each noble gas atom has a full outer shell, except for helium, which has only two electrons in its outer shell. This full outer shell provides a high level of stability, making noble gases highly unreactive.

Lack of Molecular Formation

Due to their stable electron configurations, noble gases do not easily form molecules or compounds with other elements. Their outer shells are already complete, and there is no need for additional electrons to achieve stability. As a result, noble gases exist as individual atoms, which are relatively independent of each other.

Eight Electrons in the Outer Shell

Except for helium, which has two electrons in its outer shell, the noble gases all have eight electrons in their outermost energy level. This is known as the octet rule, where elements strive to have eight electrons in their outer shell to achieve a stable electron configuration. The complete octet contributes to the stability and low reactivity of the noble gases.

This full outer shell provides a high level of stability and leads to certain characteristic properties:

• Unreactivity: Noble gases are unreactive because their full outer shells make them electronically stable. They do not readily gain, lose, or share electrons with other atoms to form compounds or molecules.
• Low Electronegativity: Noble gases have low electronegativity since they have no strong tendency to attract electrons from other atoms. This contributes to their unreactivity and reluctance to form chemical bonds.
• Lack of Molecular Formation: Due to their stable electron configurations, noble gases exist as individual atoms rather than forming molecules or compounds. Their full outer shells eliminate the need to gain or share electrons to achieve stability.

Predicting Properties from Trends

Properties within Group 0 can be predicted based on trends as you move down the group:

• Atomic Size: Atomic size generally increases as you move down the group due to the addition of energy levels or shells. This increase in atomic size leads to larger atomic radii and weaker interatomic forces, resulting in lower boiling points and melting points.
• Boiling Points: Boiling points increase down the group. This trend occurs because larger noble gas atoms have more electrons, resulting in stronger London dispersion forces (intermolecular forces). These increased intermolecular forces require more energy to overcome, leading to higher boiling points.
• Density: Density also increases down the group due to the increase in atomic mass. The larger atoms have more mass packed into the same volume, resulting in higher densities.

Example Predictions

Let's make predictions about the properties of noble gases based on the trends within Group 0:

• Helium (He): Helium has the lowest boiling point and density among the noble gases due to its smaller atomic size and lighter atomic mass.
• Neon (Ne): Neon has a higher boiling point and density compared to helium due to its larger atomic size and heavier atomic mass.
• Argon (Ar): Argon has an even higher boiling point and density compared to neon due to its larger atomic size and heavier atomic mass.
• Krypton (Kr), Xenon (Xe), and Radon (Rn): These noble gases will continue the trend of increasing boiling points and densities as you move down the group.

Conclusion

In conclusion, the noble gases in Group 0 of the periodic table are characterised by their unreactivity and stable electron arrangements. Noble gases have full outer shells or two electrons in the case of helium, making them highly unreactive and unlikely to form compounds or molecules. The boiling points of the noble gases increase with increasing relative atomic mass, indicating stronger intermolecular forces as the atoms become larger.