Why do neutrons decay after 6 minutes? If I understand correctly, Beta decay only occurs when an atom (or in this case subatomic particle) is unstable. Are neutrons consider unstable? If so why? And if they are not unstable is there is known reason as to why they decay?
 A: Free neutrons are unstable, with a half life of about 10 minutes. They almost always decay via $\beta$-decay:
$$
\text{n}^0 \rightarrow \text{p}^+ + \text{e}^-+\bar{\nu}_\text{e}
$$ 
This is the same $\beta$-decay that occurs in unstable nuclei, and is possible outside the nucleus because free neutrons are more massive than free protons. 
The situation in a nucleus is a little different, and has a great answer here.
A: Proton is the lightest baryon, neutron mass is almost same but ~1 $MeV/c^2$ heavier than proton. Baryon number must be conserved by nearly all interactions so the proton is a stable hadron. 
Neutrons by the way considerable stable in the nucleus because of strong interactions. But a free neutron may decay by a weak interaction and since proton is lighter than it, it is allowed to decay proton. 
A: Radioactive decay occurs when the parent nuclide is heavier than the daughter products, because this makes them far more stable. 
A neutron has a mass of 1.6750 x 10^-27kg whereas the combined mass of a proton and electron is only 1.673611 x 10^-27kg which is less than that of a free neutron meaning this state will be far more stable.
However, in a nucleus neutrons are stable because if they were to decay the products will most likely gain mass due to loss in binding energy as the strong interaction factors in within a nucleus for example Be-9 does not decay into B-9 because B-9 is heavier as it weighs 9.0133288amu while Be-9 only weighs 9.0121822 meaning it would need to absorb mass/energy for this decay to occur
A: Nuclear neutrons are not unstable, but free neutrons are unstable and will generally decay via beta decay, becoming a proton and releasing an electron accompanied by an electron antineutrino. Free neutrons have a mean lifetime of approximately 881.5 seconds, meaning the average lifespan of the neutrons is 881.5 seconds. The half-life of neutrons is approximately 611 seconds, meaning that after 611 seconds half of a neutron sample will have decayed, and after 611 more seconds half of the remaining will have decayed (having only a fourth left), and so on, instead of being suggested to decay after 6 minutes as the title of the question assumes.
