The core material used in ordinary lead pencils is mainly which of the following?

Introduction / Context:
Although we commonly speak of the lead in a pencil, modern pencils do not actually contain metallic lead. Instead, their writing core is made from a form of carbon that leaves dark marks on paper. This simple everyday misconception is frequently used in general science questions to test whether students know the correct material in pencil cores and to clear up confusion about the term lead pencil.

Given Data / Assumptions:

• The question asks which material is used in pencils.
• Options include silicon, phosphorus, graphite, charcoal, and None of the above.
• We assume a standard writing pencil used in schools and offices.

Concept / Approach:
The dark writing core of a pencil is composed of graphite mixed with clay and other binders, not metallic lead. Graphite is an allotrope of carbon with layers that can slide over each other, allowing the material to leave a mark on paper. The term lead pencil is historical, from a time when similar looking materials were confused with lead ore. Silicon and phosphorus are not used for this purpose, and while charcoal is also a form of carbon, it is not the standard core material of ordinary pencils.

Step-by-Step Solution:
Step 1: Recall that modern writing pencils use a graphite and clay mixture in their core. Step 2: Understand that graphite is a crystalline form of carbon with a layered structure, making it soft and able to slide off onto paper. Step 3: Recognise that the word lead in lead pencil is a misnomer; metallic lead is toxic and not used for writing cores. Step 4: Compare with charcoal, which is a different form of carbon used in art pencils and drawing sticks, not usually in standard writing pencils. Step 5: Conclude that graphite is the correct core material in ordinary pencils.

Verification / Alternative check:
Manufacturers and encyclopaedia entries consistently describe pencil leads as mixtures of graphite and clay, with varying proportions to adjust hardness. There is no mention of silicon or phosphorus in the core of everyday pencils. Art supplies may use charcoal sticks, but these are marketed separately as charcoal pencils or sticks, not as regular graphite pencils. This consistent usage confirms that graphite is the correct answer.

Why Other Options Are Wrong:
Silicon: A semiconductor material used in electronics, not for pencil cores. Phosphorus: Used in matches and certain industrial applications, not in pencil leads. Charcoal: A carbonaceous material used in drawing, but standard pencils are specifically graphite based. None of the above: Incorrect because graphite, the correct material, is explicitly listed.

Common Pitfalls:
Many people assume that because we say lead pencil, the core must contain lead. This is historically inaccurate and scientifically wrong. Some may also confuse charcoal drawing tools with graphite pencils and choose charcoal. To avoid these errors, remember the key point: ordinary pencils use a graphite and clay core, which is safer and provides controlled hardness for writing.

Final Answer:
The core of an ordinary pencil is mainly made of graphite, not metallic lead.