Among the following forms of carbon, which one is a good conductor of electricity?

Introduction / Context:
Carbon exists in several allotropes and related forms, each with distinct physical properties. Electrical conductivity is a key property that varies dramatically between these forms. While most non metallic forms of carbon are poor conductors or insulators, one allotrope in particular conducts electricity quite well and is used in electrodes and brushes. This question asks which form of carbon is a good conductor, reinforcing the link between structure and electrical behaviour.

Given Data / Assumptions:
- The options are graphite, diamond, peat, charcoal and lampblack.
- Graphite and diamond are pure allotropes of carbon with different crystal structures.
- Peat, charcoal and lampblack are carbon rich materials, often amorphous or impure.
- We focus on bulk electrical conductivity at room temperature.

Concept / Approach:
Graphite has a layered structure in which each carbon atom is bonded to three others in a hexagonal plane, leaving one electron per atom delocalised over the layer. These delocalised electrons can move freely along the layers, allowing graphite to conduct electricity. Diamond has each carbon atom bonded to four neighbours in a three dimensional network, with all electrons tightly bound in sigma bonds, making it an insulator. Peat, charcoal and lampblack are largely amorphous, contain impurities and do not show good metallic type conductivity. Therefore, graphite is the correct answer.

Step-by-Step Solution:
Step 1: Recall that graphite is an allotrope of carbon with a layered structure and delocalised electrons in each layer. Step 2: Understand that these delocalised electrons can move under an applied potential difference, giving graphite good electrical conductivity along the planes. Step 3: Contrast this with diamond, where each carbon forms four strong covalent bonds in a three dimensional network, leaving no free electrons for conduction. Step 4: Recognise that peat, charcoal and lampblack are amorphous carbon rich materials that may be somewhat conductive but are not classified as good conductors in textbook comparisons. Step 5: Conclude that among the options, graphite is the best and most widely recognised electrical conductor.

Verification / Alternative check:
Practical uses confirm this reasoning. Graphite rods are commonly used as electrodes in dry cells and electrolytic cells because they conduct electricity and are chemically relatively inert. Brushes in electric motors also use graphite because it makes good electrical contact while being soft enough not to damage metal commutators. Diamond, on the other hand, is known for hardness and electrical insulating properties, and is used in cutting tools and jewellery rather than as a conductor. Charcoal is used as a fuel and adsorbent but not as a standard electrical conductor in devices, reinforcing graphite as the correct answer.

Why Other Options Are Wrong:
Diamond is an electrical insulator because all bonding electrons are localised in strong covalent bonds. Peat is partially decomposed plant material with mixed composition and does not act as a good conductor. Charcoal and lampblack are largely amorphous carbon products used mainly as fuels, pigments or adsorbents and are not known for high electrical conductivity. While some forms of amorphous carbon can conduct to a limited extent, they do not match graphite in conductivity, and they are not the standard answer in basic chemistry questions.

Common Pitfalls:
Students may remember that both graphite and diamond are pure carbon and assume they have similar properties, forgetting how different structures influence conductivity. Another pitfall is to think that any black substance, such as charcoal, must conduct electricity like metals. Understanding that delocalised electrons in graphite layers provide a path for conduction, whereas diamond has no such delocalisation, helps clarify the difference. Visualising graphite as stacked sheets of hexagons can make this easier to remember.

Final Answer:
The form of carbon that is a good conductor of electricity is Graphite.