help with Isotopes

[jpk]

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HI
can any1 tell me wat an isotpoe is and wat the difference is between normal isotopes and radioactive isotopes

[iambored]

i'm a chem student, but from chem
isotopes are elements with the same atomic number, but different mass numbers
e.g. uranium-138 and uranium-140 (dont know if they exist, i made them up. the -number is the mass number, they both have the same atomic number coz they're both uranium)

radioactive isotopes are unstable, that is, if their atomic number is greater than 83, or if the neutron to proton (?) ratio is far away from 1:1. the further away, the more unstable it is.

remember, this is a chem defintion, so i don't know if you need all of it

[deyveed]

Radioisotopes are radioactive isotopes that give off alpha, beta or gamma rays
Thats what Excel had

[Ragerunner]

Elements with a differing amount of neutron to proton ratio?

[jpk]

ok
thx sounbds about right iambored

[Lexicographer]

A radioisotope is simply a radioactive isotope (radiates �, �, and/or �), eventually decaying to a stable isotope. Radioisotopes are formed when a stable isotope of an element has and extra neutron, either as a product of a nuclear fissure or bombardment. When decay begins a neutron will decay into a proton, electron, and negative neutrino, releasing energy in the process and turning the isotope into a different one (possibly also radioactive).

So basically, radioisotopes:
a) have extra neutrons
b) radiate �, �, and/or �
c) decay into other isotopes

edit:
1) set encoding to greek (I typed in alpha, beta and gamma)
2) if I'm wrong about something, which I feel I am, correct me immediately!

[Shoey]

Isotopes are forms of the same element with different numbers of neutrons (thus different mass number).

Unstable isotopes emit radiation to achieve a more stable state. Nuclei can be unstable for 3 main reasons:

1. Too high a mass - elements with an atomic number > 92 (ie. elements above uranium) are unstable.

There are 2 main forces acting in the nucleus: long range electrostatic repulsion between protons and the short range 'strong nuclear' force of attraction between particles in the nucleus. Neutrons sort of act as a 'nuclear glue' - spacing out protons and aiding the strong nuclear force in holding the nucleus together.

However, if the nucleus contains too many protons, an alpha particle (two protons + two neutrons) will be released to reduce the mass of the nucleus and so make it more stable.

2. Incorrect proton:neutron ratio - again, this involves the balancing act between proton electrostatic repulsion and the strong nuclear force.

If there are too many neutrons relative to protons, a neutron will be converted into a proton and an electron. The electron is then ejected from the nucleus, resulting in beta radiation.
1,0n --> 1,1p + 0,-1e

If there are too many protons relative to neutrons, a proton will form a neutron and a positron, resulting in positron emission from the nucleus:
1,1p --> 1,0n + 0,+1e

3. Too much energy in the nucleus - results in the emission of a gamma ray (pure energy) to reduce the total energy of the nucleus and make it stable. This usually occurs after one of the processes mentioned above. Isotopes with too much total energy in the nucleus (before gamma emmision) are referred to as 'metastable'. That's what the 'm' means in Technetium-99m.