Question

Identify six elements that are found in nature in uncombined form.

Short answer

Helium, Neon, Argon, Gold, Silver, and Nitrogen.

Step-by-step solution

Understanding Uncombined Elements

In nature, some elements can be found in their pure, uncombined form due to their lack of reactivity or natural occurrence in that state. These elements do not need to form compounds to achieve stability.

Analyzing Noble Gases

Noble gases, including Helium (He), Neon (Ne), and Argon (Ar), are found in nature as they rarely react with other elements due to their complete valence shell of electrons. This makes them stable in their uncombined form.

Investigating Metals

Some metals such as Gold (Au) and Silver (Ag) are often found in their free, uncombined forms in nature. These metals are known for their low reactivity, allowing them to exist in pure form.

Considering Diatomic Elements

Even though most diatomic elements are reactive, some, like Nitrogen (N₂), are naturally found in uncombined form due to their ability to form stable molecules with each other, though they often exist in combination with other elements.

Listing the Elements

Based on the analysis, six elements that are found in uncombined form naturally include: Helium (He), Neon (Ne), Argon (Ar), Gold (Au), Silver (Ag), and Nitrogen (N₂).

Key concepts

Noble Gases

Noble gases are a group of elements known for their lack of reactivity, which is why they're often found uncombined in nature. These gases include elements like Helium (He), Neon (Ne), and Argon (Ar). Their chemical stability comes from having a full valence shell of electrons, which means they have little tendency to gain or lose electrons, making them very stable. This complete electron configuration means noble gases rarely form compounds, which is why you can find them in their elemental form in the Earth's atmosphere.

• Helium (He) is not only used in balloons for its lighter-than-air property but also plays a crucial role in cryogenics due to its low boiling point.
• Neon (Ne) is famous for its bright glow in neon signs, which is a purely elemental property not reliant on compounds.
• Argon (Ar) is abundant in the atmosphere and is often used in light bulbs to prevent the oxidation of the filament.

Reactivity

Reactivity refers to how likely or vigorously an element will undergo a chemical reaction either by itself or with other elements. In general, elements that are found uncombined in nature have low reactivity. For instance, noble gases are at the far end of the reactivity scale with almost no reactivity due to their filled valence shells.

Other elements, like certain metals, have variable reactivity. Gold (Au) and Silver (Ag) have low reactivity, which allows them to remain uncombined naturally. They're resistant to corrosion and oxidation, which is why they exist in a pure state in the environment. Low reactivity helps these elements remain stable over time, even when exposed to various environmental factors.

Diatomic Elements

Diatomic elements are those that naturally pair up to form diatomic molecules. A molecule is simply two atoms bonded together. Nitrogen (N₂) is one such element, which pairs with itself to form a stable diatomic molecule. This pairing happens because two nitrogen atoms share electrons, achieving greater stability.

Though diatomic elements like hydrogen (H₂), oxygen (O₂), and halogens also exist, they are more prone to reactions than nitrogen. Nitrogen's strong triple bond between its atoms provides significant stability, making it a common uncombined gaseous element in Earth's atmosphere, comprising about 78% of it.

Metals

Certain metals, such as Gold (Au) and Silver (Ag), are typically found in their uncombined or pure state. These precious metals have been adored throughout history for their luster and rarity. Apart from their aesthetic appeal, the main reason they are found uncombined is their low reactivity. Gold and silver do not corrode easily, meaning they are less likely to form compounds with other elements.

• Gold (Au) is non-reactive with most chemicals and doesn't tarnish or rust, making it highly valuable for currency and jewelry.
• Silver (Ag) has similar resistance, known for its electrical conductivity, making it ideal for use in electronics.

Stability

Stability in chemistry typically refers to how likely an element or compound is to maintain its current state without changing through a chemical reaction. Stable elements are those that are not prone to react or combine with others, allowing them to exist in a pure form in nature.

For example, noble gases are exceptionally stable due to their filled valence electron shells, providing little incentive for them to react. Metals like gold and silver show stability because they do not easily corrode or oxidize. Similarly, diatomic molecules like nitrogen benefit from strong bonds that enhance their stability. This inherent stability is what allows these elements to remain uncombined in their natural settings.