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

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

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

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

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.

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.

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

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

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)