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Equation 39 · Part 3 · The Valley of Stability Is a Fitness Landscape

addition

(N−1,Z+1)(N-1,Z+1)
addition

What this part means

Add the term after the plus sign to the term or group before it.

Its job in the formula

Add the term after the plus sign to the term or group before it.

The passage around this formula

Each individual beta decay, then, is a single step along this fixed- A parabola: a discrete jump from one (N,Z) point to its immediate neighbor at (N-1,Z+1) or (N+1,Z-1) , taken because it lowers the mass and therefore raises binding energy per nucleon, with the released energy carried off by the emitted lepton and antineutrino or neutrino. A decay chain is a sequence of such steps, sometimes purely beta, more often threaded with alpha emissions that jump A downward by four and Z downward by two in a single move. Uranium-238’s decay chain to stable lead-206 is the standard worked example, and it takes fourteen recorded steps to complete: an alpha emission to thorium-234, a beta decay to…

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Learn the underlying idea

Addition combines quantities; subtraction measures the signed difference between them. Parentheses show what is combined before the rest of the expression is evaluated.

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Sources cited in the surrounding passage

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