Subject: Why do protons not stick together without some neutrons?

More generally, why do the protons and neutrons have to exist within a
particular range of ratios to be stable?  The strong force would not seem to
care about the types of quarks involved, only their colors.  So why can't 6
protons, for example, stick together without having between 6 and 8 neutrons
inclusive in the mix?  Likewise, there is no isotope of element 0 heavier than 1
lone neutron.

How does the residual strong force operate between neucleons in the first place?
 It's often described as being "like Van der Waals forces", which I recall is
where the molecules are weak dipoles.  But the blue quark in one particle can't
"see" a red quark in a different particle and be attracted to it, when they
happen to be arranged near each other, because the strong force is confined in
tight bundles!

Re: Why do protons not stick together without some neutrons?