Although the problem of transmuting chemical elements into each other
is much older than a satisfactory definition of the very concept of chemical
element, it is well known that the first and most important step towards its
solution was made only nineteen years ago by the late Lord Rutherford, who
started the method of the nuclear bombardments. He showed on a few ex-
amples that, when the nucleus of a light element is struck by a fast α-particle,
some disintegration process of the struck nucleus occurs, as a consequence
of which the α-particle remains captured inside the nucleus and a different
particle, in many cases a proton, is emitted in its place. What remains at the
end of the process is a nucleus different from the original one; different in
general both in electric charge and in atomic weight.
The nucleus that remains as disintegration product coincides sometimes
with one of the stable nuclei, known from the isotopic analysis; very often,
however, this is not the case. The product nucleus is then different from all
"natural" nuclei; the reason being that the product nucleus is not stable. It
disintegrates further, with a mean life characteristic of the nucleus, by emis-
sion of an electric charge (positive or negative), until it finally reaches a stable
form. The emission of electrons that follows with a lag in time the first prac-
tically instantaneous disintegration, is the so-called artificial radioactivity,
and was discovered by Joliot and Irene Curie at the end of the year 1933.
These authors obtained the first cases of artificial radioactivity by bom-
barding boron, magnesium, and aluminium with α-particles from a polo-
nium source. They produced thus three radioactive isotopes of nitrogen, sili-
con and phosphorus, and succeeded also in separating chemically the activity
from the bulk of the unmodified atoms of the bombarded substance.
Although the problem of transmuting chemical elements into each otheris much older than a satisfactory definition of the very concept of chemicalelement, it is well known that the first and most important step towards itssolution was made only nineteen years ago by the late Lord Rutherford, whostarted the method of the nuclear bombardments. He showed on a few ex-amples that, when the nucleus of a light element is struck by a fast α-particle,some disintegration process of the struck nucleus occurs, as a consequenceof which the α-particle remains captured inside the nucleus and a differentparticle, in many cases a proton, is emitted in its place. What remains at theend of the process is a nucleus different from the original one; different ingeneral both in electric charge and in atomic weight.The nucleus that remains as disintegration product coincides sometimeswith one of the stable nuclei, known from the isotopic analysis; very often,however, this is not the case. The product nucleus is then different from all"natural" nuclei; the reason being that the product nucleus is not stable. Itdisintegrates further, with a mean life characteristic of the nucleus, by emis-sion of an electric charge (positive or negative), until it finally reaches a stableform. The emission of electrons that follows with a lag in time the first prac-tically instantaneous disintegration, is the so-called artificial radioactivity,และถูกค้นพบ โดย Joliot และไอรีนกูรีที่สิ้นปี 1933ผู้เขียนเหล่านี้ได้รับกรณีแรกของกัมมันตภาพรังสีประดิษฐ์ โดย bom-barding โบรอน แมกนีเซียม และอลูมิเนียม ด้วยอนุภาคαจากโปโล-nium แหล่ง พวกเขาผลิตจึงสามกัมมันตรังสีไอโซโทปของไนโตรเจน sili-ปรับและฟอสฟอรัส ประสบความสำเร็จในการแยกสารเคมีกิจกรรมยังจากจำนวนมากยังไม่แปรอะตอมของสาร bombarded
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