Atomic Theory and Structure 1. The number of electrons and protons will always be the same in a neutral atom because they are the only negatively and positively charged respectively particles in the atom. The atomic number is the number of protons.
Abundance of elements in the Earth The following pie chart shows the percentage by mass of elements in the Earth's crust. The cosmic rays, high energy particles that pervade our Galaxy, not only provide a direct sample of cosmic matter carrying information on the processes that produce the elements, but also play a major role in the synthesis of the light elements, lithium, beryllium and boron.
As we shall see, investigations with powerful ground and space based telescopes of the abundances of these elements have led to entirely new insights into the origin of the cosmic rays. Element Genesis We now know that nucleosynthesis, the genesis of the chemical elements and their isotopes, took place both universally, shortly after the Big Bang, as well as in stars, much later.
Isotopes of the same element have the same atomic number but different masses. In general the abundance of the elements drops off exponentially as the atomic mass increases simply said: Look at the chart below and you can see a spike at atomic mass 56 These elements are approximately 10, times more abundant than their neighbors.
This is the only perturbation in the fairly smooth distribution curve. Most of the helium Heessentially all of the deuterium 2H, the heavy isotope of hydrogen and some lithium were thus produced. Lithium has two stable isotopes, 7Li and 6Li, but the relevant nuclear processes are such that the Big Bang produced significant amounts of only the heavier one.
Beryllium has one stable isotope 9Bewhile boron has two 10B and 11B. Likewise, because of the rapid expansion of the universe and the concomitant decrease of the density and temperature, neither were the heavier elements C, Oetc.
These, so-called metals, have been and still are synthesized much later in the interior of stars, as well as in stellar explosions supernovae that are the death throes of the most massive stars. The idea that the synthesis of all the elements was associated with the origin of the Universe came from George Gamow and his co-workers in the late 's.
A competing theory at that time was that of Fred Hoyle, which maintained that all the elements are synthesized in stars in galaxies. The strongest argument against an initial, universal synthesis of all the elements is the fact that very significant variations of elemental abundances are observed in stars of different ages, indicating that nucleosynthesis is an ongoing process.
Indeed, the theories of stellar evolution, supernova dynamics and Galactic chemical evolution are capable of accounting for many the observed elemental abundances at a great variety of astronomical sites. These theories are based in large part on the pioneering work in the 's of Margaret and Geoff Burbidge, Willie Fowler and Fred Hoyle, and independently that of Al Cameron.
On the other hand, there are several isotopes whose abundances cannot be understood by stellar nucleosynthesis. Even though deuterium is produced in stellar interiors, it is also very rapidly destroyed.
But in the Big Bang, deuterium produced by the capture of neutrons on protons, can survive under certain conditions on the universal density which allow the synthesized 2H to escape destruction owing to the rapid expansion of the universe.
In fact, the observed deuterium abundance in the solar system, in the Galaxy and even in distant extragalactic space, is one of the best indicators of the overall matter density of the universe. The other light elements, Li, Be and B, hold a unique place among the elements.
Even though their abundances are exceedingly low, only about that of H and about that of the next heavier elements C, N and O, they play important roles both in cosmology and cosmic-ray origin.
Li, Be and B are very easily destroyed in stellar interiors, and they are not generated in the normal course of stellar nucleosynthesis, which proceeds directly from helium to carbon via the fusion of three alpha particles helium nuclei.
Thus, until aboutthe origin of Li, Be and B remained a mystery. At that time, Hubert Reeves, Willie Fowler and Fred Hoyle suggested that these light elements could be produced in nuclear interactions of cosmic rays with the atoms of the gas and dust that pervade interstellar space in galaxies the interstellar medium.
The cosmic rays, high energy particles most likely accelerated by shock waves produced by supernovae, also pervade interstellar space. From where comes the Zirconium in artificial diamonds, the Barium that colours fireworks, the Tungsten in the filaments in electric bulbs?
Which process made the Lead in your car battery? We are literally made of star dust. We already have a way to mix in "new" Helium, Carbon and Oxygen. Low-mass stars make He, C, and O, and deliver these via stellar winds and planetary nebulae. Supernova SN Supernova Dying Star The structure of all stars is determined by the battle between gravity and radiation pressure arising from internal energy generation.
In the early stages of a star's evolution the energy generation in its centre comes from the conversion of hydrogen into helium.
Supernovae are vast explosions in which a whole star is blown up. The core again contracts until it is hot enough for the conversion of carbon into neon, sodium and magnesium.
This lasts for about 10 thousand years. No further energy can be obtained by fusion once the core has reached iron and so there is now no radiation pressure to balance the force of gravity.Write balanced nuclear equations for the following: (a) Formation of 48Ti 22 through positron emission (b) Formation of silver through electron capture (c) Formation of polonium through α decay.
Grid showing change in A and Z with different emissions Worked examples: Equations for alpha, beta and gamma decay Nuclear decay processes can be represented by nuclear equations.
The word equation implies that the two sides of the equation must ‘balance’ in some way. Apr 16, · Write the balanced nuclear equation for the formation of 95 Am through Beta- decay?
Write a balanced nuclear equation for the beta decay of each of the following? Checking if my answer is right for writing a balanced nuclear equation for polonium though alpha decay? Write a balanced nuclear equation for the decay of I?Status: Open. a.
change in color c. formation of a precipitate b. production of a gas d. change in shape c. the inward pull of gravity and outward push of thermal pressure are balanced. d. nuclear fusion is a stabilizing process. the reaction can form Fe2O3.
Write a balanced chemical equation for this reaction, and find the number of moles of oxygen. Start studying chem ch 7/ Learn vocabulary, terms, and more with flashcards, games, and other study tools. Write balanced nuclear equations for the following: (a) Alpha decay of U 92 Formation of polonium through α decay.
a) 48V = 48Ti + 0B 23 22 1 b) Cd + 0E = Ag 48 1 47 c)Rn = Po + [email protected] Write the nuclear equation for the beta decay of iodine By what process does oxygen decay to nitrogen?
a) positron emission b) alpha emission c) beta emission d) gamma emission. The alpha decay of what isotope of what element produces lead ? a) polonium b) thallium c) radon d) bismuth