| 单词 | alpha particle |
| 释义 | alpha particle A helium–4 nucleus emitted by a larger nucleus during the course of the type of radioactive decay known as alpha decay . As a helium–4 nucleus consists of two protons and two neutrons bound together as a stable entity the loss of an alpha particle involves a decrease in nucleon number of 4 and decrease of 2 in the atomic number, e.g. the decay of a uranium–238 nucleus into a thorium–234 nucleus. A stream of alpha particles is known as an alpha-ray or alpha-radiation |
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