Key Terms
Two proofs that radiation is nuclear (not atomic)
1. Radiation does not vary with chemical state, temperature, pressure, or ionization state of the atom.
Alpha (alpha)
Deflects one direction — positively charged Beta (beta): deflects opposite direction — negatively charged Gamma (gamma):
Range
The distance radiation travels through a material.
Two types of particles inside the nucleus
Protons and neutrons; collectively called nucleons.
Unified atomic mass unit (u)
Defined so that a neutral carbon-12 atom has exactly 12 u. 1 u = 1.6605 x 10^-27 kg 1 u of mass converted to energy = 93
Standard notation
(A on top left, Z on bottom left) X
Simplified notation (most common)
Use only A and X, e.g., iron-56 written as Fe-56 or ^56Fe.
Isotopes
Nuclei with the same Z (same element) but different N (different number of neutrons). Same chemistry; different masses,
Nuclear radius formula
R = r_0 * A^(1/3) where r_0 = 1.2 fm (femtometers; 1 fm = 10^-15 m)
Nuclear density
Approximately 2.3 x 10^17 kg/m^3 — about 10^14 times greater than the density of water. One cubic meter of nuclear matte
What holds the nucleus together
Two nuclear forces.
Magic numbers
Specific values of Z or N corresponding to closed nuclear shells — these nuclei are especially stable. Nuclear shell mod
Parent
The original unstable nuclide before decay. Daughter: the nuclide produced after decay.
General equation
^A_Z X* → ^A_Z X + gamma
Example
^238_92 U → ^234_90 Th + ^4_2 He