There's no single chemical formula for fertilizer because there are many different types of fertilizers! Fertilizers are typically a mixture of different compounds that provide essential nutrients to plants.

The most common nutrients in fertilizers are:

* Nitrogen (N): Promotes leaf growth and healthy green color.

* Phosphorus (P): Supports root development, flowering, and fruit production.

* Potassium (K): Helps with disease resistance, strong stems, and overall plant health.

You'll often see fertilizer formulas written like this: N-P-K. This represents the percentage of each nutrient in the fertilizer. For example, a 10-10-10 fertilizer contains 10% nitrogen, 10% phosphorus, and 10% potassium by weight.

Here are some common examples of fertilizers and their formulas:

* Ammonium nitrate: NH₄NO₃ (high in nitrogen)

* Superphosphate: Ca(H₂PO₄)₂ (high in phosphorus)

* Potassium chloride: KCl (high in potassium)

Remember, the best fertilizer for your plants depends on their specific needs and the type of soil you have. It's always a good idea to consult with a gardening expert or soil testing lab to determine the right fertilizer for your situation.