Nuclear stability is a ide that helps to identify the security of an isotope. The two main determinants that identify nuclear stability are the neutron/proton ratio and also the total number of nucleons in the nucleus.

You are watching: What determines whether or not an atom is stable

## Introduction

A isotope is an facet that has same atom number however different atom mass compared to the periodic table. Every aspect has a proton, neutron, and electron. The variety of protons is equal to the atomic number, and the variety of electrons is equal the protons, unless it is one ion. To determine the number of neutrons in an aspect you subtract the atomic number indigenous the atom mass that the element. Atom mass is represented as ($$A$$) and atomic number is stood for as ($$Z$$) and neutrons are stood for as ($$N$$).

\

The principal aspect for determining even if it is a nucleus is secure is the neutron come proton ratio. Facets with ($$ZExample \(\PageIndex1$$: Carbon Isotopes

Carbon has actually three isotopes that scientists generally used: $$\ce^12C$$, $$\ce^13C$$, $$\ce^14C$$. What is the the variety of neutron, protons, total nucleons and $$N:Z$$ proportion for the $$\ce^12C$$ nuclide?

Solution

For this particular isotope, there space 12 complete nucleons ($$A$$). Native the regular table, we have the right to see that $$Z$$ because that carbon (any the the isotopes) is 6, because of this $$N=A-Z$$ (from Equation \ref1):

\<12-6=6 \nonumber\>

The N:P ratio because of this is 6:6 or a 1:1. In fact 99% of all carbon in the earth is this isotope.

Exercise $$\PageIndex1$$: Oxygen

Identify the number of neutron, protons, total nucleons and N:Z ratio in the $$\ce^12_8O$$ nuclide?

Neutrons aid to different the protons from each other in a cell nucleus so that they carry out not feeling as solid a repulsive pressure from other.

## Isotope Stability

The graph the stable facets is generally referred to together the Band (or Belt) that Stability. The graph is composed of a y-axis labeled neutrons, an x-axis labeled protons, and a nuclei. In ~ the greater end (upper right) the the band of stability lies the radionuclides that decay via alpha decay, below is positron emission or electron capture, over is beta emissions and also elements beyond the atomic number of 83 are only unstable radioactive elements. Stable nuclei through atomic number up to about 20 have an neutron:proton proportion of about 1:1 (solid line).

Beta $$\beta^-$$ Decay: Beta $$\beta^-$$ decay accepts protons so it alters the quantity of protons and also neutrons. The variety of protons rise by 1 and also the neutron number reduce by 1. This pathway wake up in unstable nuclides that have actually too countless neutrons lie over the tape of stability (blue isotopes in number $$\PageIndex1$$). Positron $$\beta^+$$ Decay: Positron $$\beta^+$$ emission and electron catch is when the isotope gains an ext neutrons. Positron emission and also electron capture are below the tape of stability since the ratio of the isotope has more protons 보다 neutrons, think that it as there are too couple of protons for the amount of neutrons and also that is why that is below the tape of stability (yellow isotope in number $$\PageIndex1$$).

As with all degeneration pathways, if the daughter nuclides are not on the Belt, climate subsequent degeneration pathways will happen until the daughter nuclei are on the Belt.

See more: Can You Take A Hamster A Bath E A Hamster: 5 Effective Methods

Note

Although rare, four stable odd-odd nuclides exist: $$\ce^2_1H$$, $$\ce^6_3Li$$, $$\ce^10_5B$$, $$\ce^14_7N$$

## References

Olmsted III, John and also Gregory M William. Betterworld2016.orgistry fourth Edition. John Wiley and Sons Inc:NJ, 2006. Petrucci, Ralph H., wilhelm S. Harwood, F. Geoffrey Herring, Jeffry D Madura. General betterworld2016.orgistry. Pearson education Inc: NJ, 2007.