The air you breathe is made up mostly of nitrogen gas, \(\mathrm{N}_{2}\). (a) What can you say about the smallest possible piece of nitrogen gas? (b) Is nitrogen gas a compound? Explain.

When you take a breath, you're inhaling not only oxygen but also a significant amount of nitrogen gas, or \(\mathrm{N}_{2}\). This simple notation unveils an interesting concept in chemistry, that of diatomic molecules.

Diatomic molecules consist of two atoms, which can either be of the same element or of different elements, that are bonded together. Oxygen (\(\mathrm{O}_{2}\)), hydrogen (\(\mathrm{H}_{2}\)), and nitrogen (\(\mathrm{N}_{2}\)) are all examples where the two atoms are identical. These molecules are quite unique because they represent the smallest stable units of these elements in their natural form. \(\mathrm{N}_{2}\), in particular, is a gas that makes up about 78% of Earth's atmosphere.

Why does nitrogen prefer to be in diatomic form? The answer lies in the concept of elemental stability. In this diatomic state, nitrogen atoms share three pairs of electrons in a triple bond, making them incredibly stable. Simplistically, the 'pairing up' of these atoms provides a balanced and low-energy state, which is a comfortable existence for these gaseous elements.

Understanding Elemental Behavior

Elements like nitrogen tend to form diatomic molecules as a way to achieve a full outer electron shell, mimicking the configuration of noble gases, which are the epitome of chemical stability. The N-N triple bond in nitrogen gas is one of the strongest known to chemists, explaining why \(\mathrm{N}_{2}\) is a relatively inert gas, not reacting easily with other elements or compounds.

Under the umbrella of chemistry, an interesting category to explore is that of chemical compounds. These entities are made from two or more different elements that are joined by chemical bonds. A fundamental criterion for a substance to be recognized as a compound is that it can be chemically decomposed into simpler substances, reflecting a union of different identities cooperatively forming an entirely new material with distinctive characteristics.

Water (\(\mathrm{H}_{2}O\)), table salt (\(\mathrm{NaCl}\)), and carbon dioxide (\(\mathrm{CO}_{2}\)) are classic examples of chemical compounds. By comparing these with nitrogen gas, we realize that \(\mathrm{N}_{2}\) doesn't fit the bill. Since nitrogen gas is formed by two nitrogen atoms, it lacks the variety required to form a compound. This is because compounds exhibit properties entirely different from the elements they are made from, which isn't the case for \(\mathrm{N}_{2}\) as it is composed of a single element.

To appreciate the nuances of substances like nitrogen gas, it's essential to dip into the realm of elemental properties. Each chemical element on the periodic table carries a unique set of characteristics that decide how it behaves alone, and when mingling with others. Properties such as atomic number, electron configuration, and electronegativity are intrinsic 'fingerprint' features that govern elemental behavior.

Nitrogen, with its atomic number of 7, has five electrons in its outer shell and needs three more to reach the stable octet configuration. In its diatomic form, two nitrogen atoms share these electrons, allowing each other to 'think' they have fulfilled their octet, thus achieving a stable, low-energy state. This sharing of electrons highlights a fundamental biochemical principle -- elements tend to react and bond in certain ways to attain a more stable electronic configuration, a driving force behind the vast diversity of material existence.

The Unique Case of Nitrogen

Nitrogen's behavior as a diatomic molecule is a direct outcome of its elemental properties. Its tendency to form triple bonds with another nitrogen atom to create \(\mathrm{N}_{2}\) is a manifestation of its quest for stability. It's fascinating to note that while nitrogen is very inactive in its diatomic form, when transformed into compounds, such as ammonia (\(\mathrm{NH}_{3}\)), it becomes a key player in the biochemistry of life, showcasing the versatile nature of elemental properties in determining reactivity and the formation of compounds.