Which of the Following Statements Regarding Nuclear Stability Is Incorrect

Multiple Choice

Which of the following statements regarding nuclear stability is incorrect?

A) The N/Z ratio is about 1 for the first 20 elements.
B) The N/Z ratio is about 1.6 for elements at the upper end of the band of stability.
C) An N/Z ratio of 1 means that an element has an equal number of protons and electrons.
D) Elements outside the band of stability are radioactive.
E) All isotopes with Z greater than 83 are radioactive.