Atomic Spectra, Radioactivity, and Nuclear Reactions

Emission and Absorption Spectra

The elements emit energy in the form of electromagnetic radiation, but only at a few specific frequencies. Elements also absorb specific frequencies when illuminated with electromagnetic radiation.

The de Broglie Hypothesis

The de Broglie hypothesis expanded the dual behavior of radiation, suggesting that matter, especially electrons, also exhibits both particle and wave aspects. According to this hypothesis, the energy of both matter and radiation is related to the frequency (f) of the wave associated with their movement through the expression E = hf. Thus, the wavelength associated with a material particle or photon momentum is λ = h / p.

The Uncertainty Principle

The principle of indeterminacy, or uncertainty principle, states:

• It is impossible to determine simultaneously the exact values of both the position (X) and momentum (p) of a quantum object.
• It is impossible to determine simultaneously the measured value of energy (E) of a quantum object and the length of time needed for the measure.

Radioactivity

Radioactivity is the property of certain substances, called radioactive substances, to emit radiation capable of penetrating opaque materials, ionizing the air, impressing photographic plates, and exciting the fluorescence of certain substances.

• Alpha radiation consists of helium nuclei, with two protons and four neutrons.
• Beta radiation consists of fast electrons resulting from neutron decay in the nucleus, giving rise to a proton and an electron.
• Gamma rays are electromagnetic radiation (photons) of high frequency, similar to X-rays.

Nuclear Fission

Nuclear fission is a nuclear reaction in which a heavy nucleus is divided into two or more lighter nuclei when bombarded with neutrons. This process releases more neutrons and large amounts of energy.

Controlled Nuclear Fission

If the number of neutrons released in fission is very high, a material that absorbs excess neutrons is introduced to prevent an explosive reaction. This is used in nuclear power plants, submarine auxiliary generators, and rockets.

Uncontrolled Nuclear Fission

In this case, there is no control element to absorb excess neutrons, and the reaction takes place explosively, as in atomic bombs.

Nuclear Fusion

Nuclear fusion is a nuclear reaction in which two light nuclei join to form one heavier nucleus. This process releases large quantities of energy.

Controlled Nuclear Fusion

Controlled chain nuclear fusion has not yet been achieved on a profitable basis due to the technical difficulty of containing reagents, which are in a plasma state at high temperatures.

Uncontrolled Nuclear Fusion

Uncontrolled fusion occurs in hydrogen bombs. A fission bomb is used to reach the high temperature needed to carry out the fusion reaction.

The Binding Energy

The binding energy of a nucleus is the energy released when its isolated nucleons come together to form the nucleus.

Nuclear Reactions

Nuclear reactions are processes that directly involve the atomic nuclei, other than becoming.