As seen in the following reaction, O2 + 2H2 à 2H2O, what particles composing the oxygen atoms (O2) and hydrogen atoms (H2) were directly involved in making the chemical reaction which created the water molecules?

The particles that make up the oxygen and hydrogen atoms that participate in the chemical reaction are electrons.

Explanation:

The water molecule is formed by two atoms of hydrogen and one of oxygen joined by a covalent bond. The arrangement of electrons communicates an electrical asymmetry due to the electronegativity of hydrogen and oxygen. Because oxygen is more electronegative than hydrogen, electrons are closer to the oxygen atom than the hydrogen atom, which makes hydrogen atoms have a positive charge and oxygen atoms a negative one.

quartz

explanation:

the atomic number will stay the same no matter how many electrons it has, so it doesn’t decrease nor increase. it’ll only change with a different number of protons