Question

In which state does pure carbon exist at room temperature? A. gas C. solid B. liquid D. plasma

Short answer

At room temperature, pure carbon exists in a solid state (Answer: C. solid).

Step-by-step solution

Analyzing the Question

The question asks about the state of pure carbon at room temperature, which is approximately 20-25°C (68-77°F). Our goal is to identify which physical state (gas, liquid, solid, or plasma) carbon is found in under these conditions.

Reviewing Carbon Properties

Carbon is an element found with atomic number 6 on the periodic table. It is known to have several allotropes, such as diamond and graphite, which are commonly found in solid form. We need to focus on the typical state of carbon, not in extreme conditions.

Considering the Physical States

At room temperature, elements in the periodic table can exist as gases (such as oxygen), liquids (like mercury), solids (like iron), or in plasma states (under very high energy conditions). For carbon, we typically find it in solid forms such as graphite or diamond.

Determining the State at Room Temperature

Since we have established that carbon's common allotropes, diamond and graphite, are solid at room temperature and typical conditions. Also, carbon does not naturally exist as a gas, liquid, or plasma at room temperature, we conclude that its state is solid.

Choosing the Correct Answer

Based on our analysis, the correct answer to the question about carbon's state at room temperature is 'C. solid'. Both theoretical knowledge and practical observation confirm that pure carbon is found in solid form at these conditions.

Key concepts

Carbon Allotropes

Carbon is a unique element that can exist in different structural forms called allotropes. Each carbon allotrope has distinct properties due to the way carbon atoms bond together. Some of the most well-known carbon allotropes include:

• Diamond: A highly structured form where each carbon atom is bonded to four others in a 3D tetrahedral structure. This arrangement makes diamonds incredibly hard and transparent.
• Graphite: A planar form where carbon atoms are arranged in sheets of hexagonal grids. The layers are loosely held together, allowing them to slip over each other, which gives graphite its slippery feel and makes it a good lubricant.
• Graphene: A single layer of carbon atoms arranged in a hexagonal lattice. It is known for its strength and conductivity.
• Fullerenes and Nanotubes: Carbon atoms here form hollow shapes like spheres or cylinders. These structures have potential in various technological applications due to their strength and electrical properties.

At room temperature, carbon allotropes such as diamond and graphite are stable in a solid state. These variations in structures demonstrate the versatility of carbon and explain why it has so many applications across different industries.

Element Properties

Understanding the properties of carbon is essential for explaining its behavior and usefulness. Carbon is a non-metal element with the atomic number 6, found in Group 14 of the periodic table. Some key properties of carbon include:

• Covalent Bonding: Carbon has four electrons in its outer shell and can form up to four covalent bonds with other atoms, making it incredibly versatile in forming complex molecules.
• Stable Isotopes: The most common isotopes of carbon are Carbon-12 and Carbon-13, which are stable and do not undergo radioactive decay.
• High Melting and Boiling Points: As a solid, carbon can withstand high temperatures, which is why diamond is used in industrial cutting tools for its robustness.

At room temperature, elemental carbon typically maintains a solid state because of these properties, with allotropes such as graphite and diamond commonly encountered in everyday life.

Periodic Table

The periodic table is a systematic arrangement of elements based on their atomic number, electron configuration, and recurring chemical properties. Carbon, with its unique characteristics, is a prominent member of this table. Here are a few critical insights related to carbon's position:

• Group 14: Carbon is located in this group, which is also known as the carbon group. This group includes elements like silicon and tin, which also have four valence electrons, allowing diverse bonding and chemical reactions.
• Non-metal Nature: Despite being grouped with both nonmetals and metalloids, carbon exhibits typical non-metal properties such as forming covalent bonds and existing at room temperature in solid forms like diamond and graphite.
• Atomic Number 6: The atomic number indicates there are six protons in the nucleus of a carbon atom. This simple fact positions carbon in a unique place where it can form complex organic compounds essential to life.

The placement of carbon in the periodic table helps us comprehend its ability to form various compounds, and its utility across scientific disciplines—from organic chemistry to materials science.