Register to reply

Why is Cobalt-60 radioactive?

by americast
Tags: cobalt60, radioactive
Share this thread:
Oct4-13, 11:23 PM
P: 23
I have heard that if n/p ratio of a substance becomes more than 1.56, it becomes radioactive. But for Cobalt-60, n/p= 1.22. Yet it is radioactive. Why is that so?

Thanx in advance...
Phys.Org News Partner Physics news on
Researchers demonstrate ultra low-field nuclear magnetic resonance using Earth's magnetic field
Bubbling down: Discovery suggests surprising uses for common bubbles
New non-metallic metamaterial enables team to 'compress' and contain light
Simon Bridge
Oct5-13, 12:04 AM
Sci Advisor
HW Helper
Simon Bridge's Avatar
P: 12,739
That is only a rule of thumb.
Co60 is radioactive because it is energetically favorable for it to be so.
Oct5-13, 01:39 AM
P: 384
There is a simple rule named Mattauch rule with just 2 exemptions:

Out of two isotopes with same mass and whose proton number differs by one, at least one must be radioactive.

The 2 exemptions are:
Antimony-123 and tellurium-123 are both stable
Tantalum-180 and hafnium-180 are both stable (Also tungsten-180 decays by alpha decay, not electron capture as it should by Mattauch rule).

A consequence of Mattauch rule is:
By Mattauch rule, the only stable isotopes with odd number of protons and neutrons are the 4 light isotopes D, Li-6, B-10 and N-14. All others should be radioactive.
Tantalum 180 is violating Mattauch rule and so is the 5th stable odd-odd isotope. There are still just these 5. Cobalt 60 is odd-odd, and is not one of these 5 stable isotopes, so it is radioactive.

Oct5-13, 03:31 AM
P: 23
Why is Cobalt-60 radioactive?

Thanx a lot...!

Register to reply

Related Discussions
Cobalt Colours Biology, Chemistry & Other Homework 1
Half-life exercise, radioactive/non-radioactive ratio Introductory Physics Homework 4
Making Cobalt Blue by Sintering Alumina & Cobalt monoxide...? Chemistry 2
CObalt 60 High Energy, Nuclear, Particle Physics 0
Nuclear Chemistry: Kinetics of Radioactive Decay and Radioactive Dating Biology, Chemistry & Other Homework 1