Here's how to determine the number of protons and electrons in a molecule of H₂O₂ (hydrogen peroxide):

1. Identify the Elements:

* Hydrogen (H)

* Oxygen (O)

2. Atomic Numbers:

* Hydrogen has an atomic number of 1 (1 proton)

* Oxygen has an atomic number of 8 (8 protons)

3. Number of Protons:

* There are 2 hydrogen atoms (2 x 1 proton = 2 protons)

* There are 2 oxygen atoms (2 x 8 protons = 16 protons)

* Total Protons: 2 + 16 = 18 protons

4. Number of Electrons:

* In a neutral molecule, the number of protons and electrons is equal.

* Total Electrons: 18 electrons

Therefore, a molecule of H₂O₂ has 18 protons and 18 electrons.