alpha particle

Examples of alpha particle in the following topics:

• Modes of Radioactive Decay

  • Alpha particles carry a positive charge, beta particles carry a negative charge, and gamma rays are neutral.
  • Alpha particles have greater mass than beta particles.
  • By passing alpha particles through a very thin glass window and trapping them in a discharge tube, researchers found that alpha particles are equivalent to helium (He) nuclei.
  • An alpha particle (α\alpha) is made up of two protons and two neutrons bound together.
  • Alpha particles can be completely stopped by a sheet of paper.

• Balancing Nuclear Equations

  • Common light particles are often abbreviated in this shorthand, typically p for proton, n for neutron, d for deuteron, α representing an alpha particle or helium-4, β for beta particle or electron, γ for gamma photon, etc.
  • This fits the description of an alpha particle.
  • This could also be written out as polonium-214, plus two alpha particles, plus two electrons, give what?
  • In order to solve this equation, we simply add the mass numbers, 214 for polonium, plus 8 (two times four) for helium (two alpha particles), plus zero for the electrons, to give a mass number of 222.
  • Describes how to write the nuclear equations for alpha and beta decay.

• Isotopes

  • Unstable isotopes most commonly emit alpha particles (He2+) and electrons.

• Indoor Pollution: Radon

  • Radon and its daughters continue to decay in the lungs, releasing alpha and beta particles that can damage cellular DNA and result in lung cancer.

• Reactions at the α-Carbon

  • Many aldehydes and ketones undergo substitution reactions at an alpha carbon, as shown in the following diagram (alpha-carbon atoms are colored blue).
  • If the alpha-carbon is a chiral center, as in the second example, the products of halogenation and isotopic exchange are racemic.
  • First, these substitutions are limited to carbon atoms alpha to the carbonyl group.
  • Cyclohexanone (the first ketone) has two alpha-carbons and four potential substitutions (the alpha-hydrogens).
  • This is demonstrated convincingly by the third ketone, which is structurally similar to the second but has no alpha-hydrogen.

• Allotropes of Carbon

  • Amorphous graphite: fine particles, the result of thermal metamorphism of coal; sometimes called meta-anthracite
  • The two known forms of graphite, alpha (hexagonal) and beta (rhombohedral), have very similar physical properties (except that the layers stack slightly differently).
  • The alpha form can be converted to the beta form through mechanical treatment, and the beta form reverts to the alpha form when it is heated above 1300 °C.

• Particle Accelerator

  • A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds within well-defined beams.
  • A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams.
  • While current particle accelerators are focused on smashing subatomic particles together, early particle accelerators would smash entire atoms together, inducing nuclear fusion and thus nuclear transmutation.
  • This occurs either through nuclear reactions in which an outside particle reacts with a nucleus, which can be supplied by a particle accelerator, or through radioactive decay, where no outside particle is needed.
  • Electrostatic accelerators use static electric fields to accelerate particles.

• Root-Mean-Square Speed

  • The root-mean-square speed measures the average speed of particles in a gas, defined as $v_{rms}=\sqrt{\frac{3RT}{M}}$ .
  • According to Kinetic Molecular Theory, gaseous particles are in a state of constant random motion; individual particles move at different speeds, constantly colliding and changing directions.
  • We cannot gauge the velocity of each individual particle, so we often reason in terms of the particles' average behavior.
  • Particles moving in opposite directions have velocities of opposite signs.
  • Since the value excludes the particles' direction, we now refer to the value as the average speed.

• Distribution of Molecular Speeds and Collision Frequency

  • The movement of gaseous particles is characterized by straight-line trajectories interrupted by collisions with other particles or with a physical boundary.
  • Consider a closed system of gaseous particles with a fixed amount of energy.
  • In theory, this energy can be distributed among the gaseous particles in many ways, and the distribution constantly changes as the particles collide with each other and with their boundaries.
  • By understanding the nature of the particle movement, however, we can predict the probability that a particle will have a certain velocity at a given temperature.
  • As the temperature increases, the particles acquire more kinetic energy.

• Enolate Intermediates

  • Many of the most useful alpha-substitution reactions of ketones proceeded by way of enolate anion conjugate bases.
  • Esters and nitriles are even weaker alpha-carbon acids than ketones (by over ten thousand times), nevertheless their enolate anions may be prepared and used in a similar fashion.
  • The presence of additional activating carbonyl functions increases the acidity of the alpha-hydrogens substantially, so that less stringent conditions may be used for enolate anion formation.
  • The influence of various carbonyl and related functional groups on the equilibrium acidity of alpha-hydrogen atoms (colored red) is summarized in the following table.
  • Note that each of these compounds has two acidic alpha-hydrogen atoms (colored red).