Chemical element isotopes: specifically the elements without any stable isotopes are technetium (atomic number 43), promethium (atomic number 61), and all observed elements with atomic numbers greater than 82. Of the 80 elements with at least one stable isotope, 26 have only one single stable isotope. The mean number of stable isotopes for the 80 stable elements is 3.1 stable isotopes per element. The largest number of stable isotopes that occur for a single element is 10 (for tin, element 50). The mass number of an element, "A", is the number of nucleons (protons and neutrons) in the atomic nucleus. Different isotopes
SN 2002cx is extinct in B-V color by 0.034 magnitudes from dust in Milky Way. SN 2002cx is similar to SN 1999ac in B-V at max, but also at times as late as 50 days after max which is unexpected as the two supernovae evolve differently at late times. SN 2002cx has a B-V color of -0.04±0.04 at 4 days before max, and 0.04±0.05 at the time of max in the B-band which is bluer than SN 1991bg at the same time. The color of SN 2002cx is consistent with Lira-Phillips law at late times. The V-R color of SN 2002cx evolves