If neutrons decay into proton, electron and (anti)neutrino of electron type, then is it safe to say that atoms are protons, electrons and neutrinos?
3$\begingroup$ Something to ponder: nuclei with too many protons are unstable to positron emission, wherein a proton "turns into" a neutron, a positron, and a neutrino. Do you see where this might lead to an infinite recursion of infinitely many particles if things really consisted of their decay products? $\endgroup$– user10851Nov 28, 2014 at 0:18
$\begingroup$ I do see. I was trying to express my intuition on this matter to @Frederic Brünner also. These findings must have turned tide for most audience who wanted to see "components". $\endgroup$– GianniTeeNov 28, 2014 at 14:23
No. The decay products of a certain particle are not equivalent to its constituents. This is evident especially in the context of fundamental particles: quarks can decay into other particles, but that does not mean that a quark is not elementary (see my answer to this question).
Nuclei are made of neutrons and protons, which in turn consist of quarks and gluons, and hence, on an elementary level, atoms are made of electrons, quarks and gluons.
$\begingroup$ I read your comment. It is very interesting. You say that decays obey conservation laws, which feels like the cornerstone of sanity. Conversions of particles exhibit perhaps equal probability to go one way, the reverse way, or a completely different way. Hence, the "components" are undefined or undecided. Right? $\endgroup$ Nov 27, 2014 at 23:40
3$\begingroup$ @GianniTee: The point is that decay in particle physics is not equivalent to "breaking apart into constituents", but it could more accurately be imagined as a conversion. Probabilities are in general not symmetric under reversal: their calculation is a very non-trivial task, often with unforeseeable outcome. $\endgroup$ Nov 27, 2014 at 23:47
1$\begingroup$ ...and from photons, Z and W(+/-) bosons? $\endgroup$– peterhNov 28, 2014 at 16:10
$\begingroup$ @Peter: Indeed, atoms are 'made of' photons, Z and W bosons gluons just as they're made of gluons. I would personally exclude all. This answer is indeed inconsistent in stating just gluons. $\endgroup$– JBSnorroNov 28, 2014 at 20:44
$\begingroup$ Still, books suggest a table of elementary particles that includes photons, electrons, etc. $\endgroup$ Nov 29, 2014 at 19:26
No. The atoms are protons, electrons and neutrons. The fact that neutrons beta decay into a proton + electron + electron antineutrino does not mean that neutrons are made of a proton and electron and a neutrino.
According to Grand Unification Theory, protons can decay into electron (even at low energy; just the probability is very low). It doesn't mean you can replace proton with electron.