Summary Atom and Atomic Nucleus/ RADIOACTIVITY, RADIOACTIVE BEAMS/ Radioactivity structure and Important Notes about Physics
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Course
Physics
Institution
Fifth Year / 11th Grade
This document serves as a comprehensive guide, propelling you towards a deeper understanding of the radioactivity and the intricacies of radioactive decay and beam applications within the framework of quantum mechanics.
This document caters to:
Upper-level undergraduate students with a founda...
Atom and atomic nucleus -
Important notes, the history of Radioactivity, Types of
radioactive beams & Atomic system
In 1896, the French physicist Henri Becquerel discovered the phenomenon of
radioactivity. While doing research on uranium salt, he observed that uranium
salt emits rays invisible to the eye that have the ability to darken the
photographic plate and ionize the air.
In 1898, Pierre Curie and his wife Maria Curie determined that, in addition to
uranium, a number of other elements (polonium, radium, thorium, and etc.) also
has strong irradiation ability. They called this radiation radioactivity.
Numerous experiments carried out have shown that the property of natural
radioactivity is associated only with the composition and structure of the atomic
nucleus of the element. External factors (mechanical pressure, temperature,
electric and magnetic fields, etc.) does not affect this property.
• The phenomenon of self-irradiation of atomic nuclei without external
influences is called natural radioactivity, and the radiation that occurs is
called radioactive radiation.
In 1899, under the leadership of the English physicist Ernest Rutherford, the
physical nature of radioactive radiation was studied. It was found that the
radioactive radiation of radium has a complex composition: the radiation consists
of a flood of different particles. When these particles pass the flood through the
magnetic field, they tend in different directions under the influence of the Lorentz
force. Since some of the rays consist of a flood of unladen particles, they continue
their way in their original direction – they were called γ (gamma)-radiation. Since
some of the rays consist of a stream of positively charged particles, they tend
from their previous direction to the direction of the thumb of the left hand. This
radiation was called α (alpha)-radiation. the third part, called β (betta)-radiation,
is a flood of negatively charged particles, so they tend in the opposite direction to
α-radiation.
, It has been established that α-radiation consists of a Helium (He) core flood. Its
penetrating ability is poor and is retained even by a sheet of paper with a
thickness of 0.1 mm. β-radiation is a flood of electrons with a very large velocity.
The penetrating ability of these particles is relatively large – a zinc plate several
millimeters thick can block β-rays. γ-radiation is electromagnetic radiation. Since
it is electrically neutral, it is not subject to the influence of electric and magnetic
fields. The penetrating ability of these beams is very high: lead with a thickness of
1cm, concrete with 5cm and glass plate with 10cm can reduce its impact by 2
times, but cannot fully absorb it.
The Atom is a complex, coherent system-
Thomson model of the atom : Scientists have known since the end of the
nineteenth century that an atom has an electroneutical structure consisting of an
equal number of positively and negatively charged particles. English physicist Sir
Joseph John Thomson discovered the electron in 1897 and found that the mass of
the electron is ≈ 2000 times smaller than the mass of a hydrogen (H) atom. Based
on this fact, on the one hand, and on the other, on the fact that the atom is
electrically neutral, Sir Thomson puts forward the first model of the structure of
the atom in 1903. According to this model, the atom is spherical with a radius of
about 10-10 . Positive charges are distributed with equal density over the entire
mass of that sphere, while negatively charged electrons are located within this
mass as "Plum Pudding” :
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