Decades: 270s BC 260s BC 250s BC 240s BC 230s BC - 220s BC - 210s BC 200s BC 190s BC 180s BC 170s BC
Years: 231 BC 230 BC 229 BC 228 BC 227 BC - 226 BC - 225 BC 224 BC 223 BC 222 BC 221 BC
... an atomic nucleus ejects an alpha particle and transforms into a nucleus with mass number[?] 4 less and atomic number 2 less. For example
23892U → 23490Th + ...
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