It's impossible to say exactly how many elements are mentioned in Bill Nye the Science Guy's chemical reactions episodes without a detailed analysis of every episode. However, we can make some educated guesses:

* Common Elements: Bill Nye likely discusses the most common elements involved in everyday chemical reactions, such as:

* Carbon (C): Found in organic molecules and fuels.

* Hydrogen (H): A component of water, fuels, and many organic molecules.

* Oxygen (O): Essential for combustion and respiration.

* Nitrogen (N): Found in air and in many organic molecules.

* Sodium (Na): Reacts vigorously with water.

* Chlorine (Cl): Found in many household cleaners.

* Calcium (Ca): Essential for bones and teeth.

* Iron (Fe): Essential for blood and metal production.

* Periodic Table Focus: Bill Nye probably focuses on the common elements and those related to specific reactions he demonstrates. He might not discuss all 118 elements, but he would likely mention a fair number from various parts of the periodic table.

* Specificity Varies: Depending on the specific episode, the number of elements discussed will vary. Some episodes might focus on a small number of elements related to a specific reaction, while others might introduce a wider range of elements.

To get a more accurate answer, you would need to:

1. Identify the specific Bill Nye episodes focused on chemical reactions.

2. Watch the episodes and make a list of all the elements mentioned.

Let me know if you have specific episode titles or topics in mind, and I can help you narrow down the elements mentioned!