# How many elementary particles are contained in a molecule of $H_2O$?

I was wondering about how many elementary particles form up one molecule of $H_2O$.

What I thought of is the following:

Hydrogen : 0 neutrons, 1 electron, 1 proton; electron is elementary and proton is formed of 3 quarks so hydrogen (H) is 4 particles and hence $H_2$ is 8 particles. Same thought for Oxygen 8 neutrons each 3 quarks, 8 protons each 3 quarks, 8 electrons the total for oxygen is 56.

So Total number of particles in $H_2O$ is 64 fundamental particles.

Is that correct?

• That's what I get. Jul 25 '18 at 8:03
• For the real constituents this is accurate. But note that only about 1% of the protons mass is generated by the constituent quarks and therefore the Higgs mechanism. The other 99% are kinetic energy of the quarks and the binding energy of the gluon field. So you could say that there also countless gluons within a proton. Jul 25 '18 at 8:19
• Physics SE: What's inside a proton? A similar logic would apply to neutrons.
– user191954
Jul 25 '18 at 10:51

Saying $H_2O$ is 64 fundamental particles is largely right.
One trivial problem is that sometimes the oxygen is another stable isotope like $^{17}O$ or $^{18}O$ with 1 or 2 extra neutrons, adding 3 or 6 quarks.