#3

Strong nuclear force is a very strong force of attraction given off by all nuclear particles which acts over a very small distance. This attempts to hold the nucleus together. Electrostatic force. It is much weaker than the SNF but acts over a much larger distance. Only acts on charged particles. In the nucleus where all of the charged particles have a similar charge, the EMF attempts to push the nucleus apart. #5 The primary factor in determining nuclear stability is the PROTON : NEUTRON RATIO.

The most stable ratio is about 1:1 for small atoms, and gradually increases to about 1:1.5 for larger atoms. See pg 866.

A secondary cause for a nucleus to be unstable is the nucleus being to large… BISMUTH-209 If a particle has more than 83 protons or a mass number greater than 209 it is too big to be stable # 9. Isotopes not in the band of stability undergo spontaneous changes (transmutations) to other, more stable, isotopes. # 10: Certain isotopes for each element are stable…these do not change. Other isotopes are unstable (we call them radioactive isotopes or radioisotopes).

# 12 Radioactive decay is when an unstable nucleus shoots out (radiates) small pieces of their nuclei (radiation). #13 Alpha decay: Nucleus too big mass=4 amu charge = +2 Beta decay: Too many neutrons per proton mass = 0 charge = -1 Positron decay: Too few neutrons per proton mass = 0 charge = +1 Electron capture: Too few neutrons per proton mass = 0 charge = -1 Gamma Ray: accompanies all other nuclear changes no mass or charge just energy # 16. We find mainly stable isotopes, because over the eons, unstable ones have transmuted themselves into stable ones. We call these transmutations nuclear changes or nuclear reactions.

Over time there will be less and less radioactive material in nature because it is constantly decaying into stable material.

In a nuclear reaction, the identity of the elements can change, but the total mass and amount of charge must stay the same. To ensure that our representative equation shows this we must balance our nuclear equations. To do so we must: a. Write the chemical symbol for all reactants (things as they exist before the change) and products (things as they exist after the change) separated by an arrow including their atomic number written as a subscript to the left of the symbol, and their atomic mass written as a superscript to the left of the symbol. b. Ensure that the total atomic numbers on both sides of the equation (arrow) are equal, and that the total atomic masses on both sides of the equation are equal. --They have too little Binding Energy per nucleon When an atom forms from sub-atomic particles, the atoms weigh less than the sum of the particles. This “lost” weight (mass defect) is converted to energy according to e=mc2. This energy must be replaced to each nucleon in order for an atom to break apart, so the lower this energy per nucleon, the more unstable the isotope.

Synthetic (man-made) decay

We can cause isotopes otherwise stable isotopes to decay by shooting them with small nuclear particles. They will usually give off protons, or neutrons, or both. These particles which are given off can then create a self sustaining decay if their is enough of the original isotope. (critical mass)