In safety matches, which chemical substance is mainly used on the specially prepared striking surface of the matchbox?

Introduction / Context:
Safety matches are designed so that they ignite only when rubbed against a specially prepared striking surface, making them safer than older friction matches. The chemistry behind safety matches involves separation of fuel, oxidising agent and an easily ignitable form of phosphorus. This question focuses on which form of phosphorus is used on the striking surface of the matchbox, an idea often highlighted in basic chemistry and general science.

Given Data / Assumptions:
- The context is modern safety matches, not older white phosphorus based matches.
- The match head and the striking surface contain different chemical components.
- Options include red phosphorus, white phosphorus, potassium sulphate and sulphur.
- The question asks specifically about the substance applied on the striking surface, not in the match head itself.

Concept / Approach:
In safety matches, the match head typically contains an oxidising agent such as potassium chlorate, together with sulphur or other fuels and binders. The striking surface on the side of the box contains red phosphorus mixed with powdered glass and an abrasive material. When the match is struck, friction converts some red phosphorus to white phosphorus vapour, which ignites and then sets off the oxidising agent and fuel in the match head. White phosphorus is highly toxic and not used as a stable coating. Potassium sulphate and sulphur play other roles and are not the main ingredient on the striking surface in standard descriptions.

Step-by-Step Solution:
Step 1: Recall that safety matches are formulated so that phosphorus is kept separate from the oxidising agent until striking occurs. Step 2: Remember that red phosphorus is a relatively stable, less toxic allotrope used on the striking surface of the matchbox. Step 3: Recognise that when the match is struck, friction converts a small amount of red phosphorus into more reactive white phosphorus, which ignites easily. Step 4: Understand that white phosphorus itself is too reactive and toxic to be used as a stable coating on the outside of matchboxes. Step 5: Conclude that red phosphorus is the correct answer for the substance applied on the striking surface.

Verification / Alternative check:
Standard school textbooks and general science books describe the composition of safety matches by separating the roles of the match head and the striking surface. They explicitly state that the striking surface contains red phosphorus, powdered glass and glue. This configuration reduces accidental ignition compared with older matches, which used white phosphorus directly in the head and were hazardous. The repeated mention of red phosphorus in this context provides strong support for the answer.

Why Other Options Are Wrong:
White phosphorus is very reactive and toxic and is not used as a safe external coating in modern safety matches. Potassium sulphate is a neutral salt and is not the key friction sensitive ingredient on the striking surface. Sulphur is used in the match head as a fuel component rather than on the striking strip. The statement that no option is correct is also wrong because common descriptions clearly identify red phosphorus as the major ingredient on the striking surface of safety matches.

Common Pitfalls:
A common confusion is to think that phosphorus must be in the match head because that is the part that visibly burns. In safety matches, however, the design intentionally separates red phosphorus onto the box to improve safety. Another pitfall is to mix up red and white phosphorus, forgetting that white phosphorus is the more dangerous allotrope. Remembering the phrase red phosphorus on the striking surface can help keep this detail clear for examinations and practical understanding alike.

Final Answer:
In safety matches, the substance used on the special striking surface of the matchbox is Red phosphorus.