Isotope
Even and odd nucleon numbers
The proton:neutron ratio is not the only factor affecting nuclear stability. It depends also on evenness or oddness of its atomic number Z, neutron number N and, consequently, of their sum, the mass number A.

Isotope

Section Title: Even and odd nucleon numbers
Table Section Text: The proton:neutron ratio is not the only factor affecting nuclear stability. It depends also on evenness or oddness of its atomic number Z, neutron number N and, consequently, of their sum, the mass number A.

p,n	EE	OO	EO	OE	Total

Stable	146	5	53	48	252

Long-lived	22	4	3	5	34

All primordial	168	9	56	53	286

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