Question

Carbon is usually classified as a nonmetal. However, the graphite used in "lead" pencils conducts electricity. Look at a pencil, and list two nonmetallic properties of graphite.

Short answer

Graphite is brittle and has luster, nonmetallic properties.

Step-by-step solution

Identify Graphite's Group

Graphite is an allotrope of carbon, which belongs to Group 14 in the periodic table. Historically, carbon and its allotropes are classified as nonmetals. In this context, properties typically associated with nonmetals must be considered for graphite.

Discuss Brittleness

One common property of many nonmetals, including graphite, is brittleness. Graphite can break or shatter under stress or pressure, rather than deforming like metals. This brittleness is indicative of nonmetallic behavior.

Examine Luster Property

While some nonmetals are dull, graphite exhibits a metallic luster that is somewhat atypical but still consistent with nonmetals given their diversity in appearance range. The luster does not alter its classification as a nonmetal.

Evaluate Electrical Conductivity

Although graphite conducts electricity, unlike most nonmetals, this conductivity arises from its unique crystalline structure where electrons can move freely along planes. This characteristic is an exception and does not conceal its basic nonmetallic properties.

Key concepts

Brittleness in Nonmetals

Graphite, a well-known form of carbon, displays a characteristic brittleness common among nonmetals. This property means that graphite can easily crack, break, or shatter when subjected to force or pressure. Unlike metals, which tend to deform or bend under stress, nonmetals lack the ability to absorb significant mechanical energy without fracturing.

• This brittleness is primarily due to the strong directional bonds within its structure.
• These bonds hold its layers firmly but weakly connected to each other, making it easy to snap apart.

Despite being brittle, the structure of graphite allows its layers to slide over one another which is why it feels smooth to touch and is used in writing pencils.

Graphite Conductivity

One of the interesting exceptions to the rules surrounding nonmetals is graphite's ability to conduct electricity. Graphite conducts electricity due to its unique crystal structure.

• It consists of layers of carbon atoms arranged in hexagonal lattices.
• In these layers, one electron from each carbon atom is free to move, allowing electricity to flow.

This movement happens within the planes of these layers, making graphite an excellent conductor parallel to its layers, unlike most nonmetals that are typically insulators. It’s important to note that while graphite's conductivity aligns with metals, it doesn't change its classification as a nonmetal because its core chemical properties remain nonmetallic.

Luster in Nonmetals

Though many nonmetals are known for their lack of shine, graphite presents a somewhat metallic luster. This shiny surface can seem puzzling since we might expect nonmetals to appear dull.

• The luster of graphite is due to the electron's ability to reflect light rays from its surface effectively.
• This characteristic is not unique to graphite, as some nonmetals can display a sheen or shine.

Hence, having a luster does not conflict with graphite's classification as a nonmetal, highlighting the diversity in physical appearances that nonmetals can show.

Carbon Allotropes

Carbon is a notable element because it exists in several different forms known as allotropes. Each allotrope, including graphite, exhibits unique properties owing to differences in atomic arrangements and bonding.

• Graphite and diamond are the most famous carbon allotropes, with vastly different properties.
• While diamond is incredibly hard with each carbon atom tightly bonded, graphite consists of layers that can easily slide, related to its softness and use as a lubricant.
• Fullerenes and graphene are other intriguing carbon allotropes, each with their own set of distinctive attributes.
• The ability of carbon to exist in multiple forms is because of its versatile bond formation capabilities, facilitated by its four valence electrons.

Just from this comparison, it’s evident how versatile carbon can be, adapting to form materials ranging from the rigid to the conductive, highlighting the importance of structural arrangement in its properties.