1. Do Now, Agenda Take out Avg Mass HW to be checked
Work on Avg Mass Candy Lab, turn in
Nuclear Stability
Unit 6A Quest TUES 11/10

2. Isotopes=different versions of the same element
They have the same # protons but a different # neutrons

3. Nuclear Reaction:
A reaction that involves a decay (break down) in the nucleus of an atom.
Nuclear reactions occur because the nucleus of an atom is unstable

4. Inside the nucleus of atoms…
There are 2 subatomic particles in the nucleus: protons+ neutrons
Protons have a positive charge, whereas neutrons have neutral or no charge.
As atomic # increases, the # of protons increases, & nuclear charge increases. This causes more repulsions between protons within the nucleus.
Neutrons help stabilize the nucleus by reducing the repulsive forces between protons

5. Stability of the Nucleus Whether a nucleus of an atom is stable or unstable depends on the ratio of protons to neutrons in the nucleus.

6. Nuclear Stability Questions
Do the number of electrons affect the stability of the nucleus? Explain.
Examine the elements with atomic numbers between 1 and 20. In general, what is the neutron to proton ratio needed for the nucleus to be stable?
1:1 (1 neutron for every 1 proton)
1.5:1 (3 neutrons for every 2 protons)
Examine the elements with atomic numbers between 20 and 82. In general, what is the neutron to proton ratio needed for the nucleus to be stable?
Use the chart above to answer the following question: If an atom has an atomic number greater than ____________, its nucleus will be unstable no matter what.

7. Nuclear Stability Nuclear Stability Band of Stability
Depends on # of neutrons to protons in nucleus
“Stable Number” is different based on on how big the atom is
Band of Stability
A graph showing all the stable isotopes for each element
Atoms that fall “between the band” are stable

8. Radioactivity
Smaller, stable elements have at least 1 neutron for every proton
Larger, stable elements usually have about 3 neutrons for every 2 protons

9. General Stable Neutron to Proton Ratios
H  K: 1 to 1 ratio (1 N for every 1 P)
Ca  Bi: 1.5 to 1 ratio (3 N for every 2 P)
Elements with atomic number greater than 84 (Po) are generally unstable and radioactive (regardless of the # of N:P)