Just being a bit pedantic ... more than half? Atoms typically have more neutrons than protons, and neutrons also weigh slightly more. Surely I'm >50% neutrons by mass?
Agreed -- I should have gone with "roughly half" or "almost half". As I wrote last night, I incorrectly recalled that n/p is often below 1 -- if I had thought for a moment about high-Z nuclei, the error would have been obvious.
It’s probably close to 50%. 80% of your mass is water and carbon. Hydrogen makes up 10% taken by itself but generally didn’t have a neutron which balances out the comparatives rare bigger elements with more neutrons.
A great place for a reader to begin to reach their own conclusions is here: https://en.wikipedia.org/wiki/Neutron%E2%80%93proton_ratio
Thank you for the correction.