Atomic number conservation

OC-Decay. In a-decay the parent atom of atomic number Z and mass M emits an a-particle, a He nucleus having Z = 2 and A = 4 and becomes an atom having atomic number Z — 2 and mass A — 4. From the conservation of energy, the energy of the a-particle is... 

Chemical reactions are represented by chemical equations, which identify reactants and products. Formulas of reactants appear on the left side of the equation those of products are written on the right In a balanced chemical equation, there are the same number of atoms of a given element on both sides. The same situation holds for a chemical reaction that you carry out in the laboratory atoms are conserved. For that reason, any calculation involving a reaction must be based on the balanced equation for that reaction. 

The number of molecules of H2 needed to react with one molecule of 02 is the number needed to produce two molecules of H20. If two molecules of HaO are formed, four atoms of hydrogen are needed. Two molecules of H2 contain four atoms of hydrogen. Remember, in chemical reactions, atoms are conserved. 

Atomic velocity distribution, 130,131 Atomic volume, 94, 98 alkali metals, 94 halogens, 97 inert gases, 91 third-row elements, 101 Atomic weight, 33 table, inside back cover Atoms, 21 conservation of, 40 electrical nature of, 236 measuring dimensions of, 245 Avogadro, Amadeo hypothesis, 25, 52 hypothesis and kinetic theory, 58 law, 25 number, 33 Azo dyes, 344... 

STRATEGY Write the nuclear equation for each reaction, representing the daughter nuclide as E, with atomic number Z and mass number A. Then find Z and A from the requirement that both mass number and atomic number are conserved in a nuclear reaction, (a) In a decay, two protons and two neutrons are lost. As a result, the mass number decreases by 4 and the atomic number decreases by 2 (see Fig. 17.7). (b) The loss of one negative charge when an electron is ejected from the nucleus (Fig. 17.8) can be interpreted as the conversion of a neutron into a proton within the nucleus ... 

Charge number and mass number are conserved in nuclear reactions, so the missing components can be identified from the atomic numbers of the elements and the charge and mass numbers of elementaiy particles. 

The amount of boron required for BNCT can be estimated using the neutron capture cross sections, which are atomic properties, and thus pertain to the number, and not the mass, of the atoms present. Conservative estimates for successful therapy result in boron concentrations of around 20 ppm in tumor tissue, to at least match the dose liberated by neutron capture reactions in the other elements of biological tissue. This would correspond to around 109 boron-10 atoms per cell, assuming that one cell corresponds to 10-9 g. 

All aerosol products identified in the sm( chamber can be reasonably explained in terms of the O Neal and Blumstein and Criegee mechanisms, as is illustrated in Figure 3-11 for Qrclohexene. The major difference between alkenes and cyclic olefins lies in the fact that, after opening of the ( clic olefin double bond, the original number of carbon atoms is conserved and the chain carries both the carbonyl group and the biradical intermediate, whose further reactions lead to the observed difunctional compounds. 

In order to determine the averaged occupation numbers n,. for the considered atoms (3 < Z 30), we have solved numerically the system of highly non-linear equations composed from the particle number conservation condition (17) and the plateau condition (24). It was found that the condition (25) is fulfilled with desired accuracy (with less than 1% discrepancy for 5iEhfr) for values of M > 35, and the roots Yo and X found at M = 35 allow a correct determination of the n. ... 

Conservation of mass and charge are used when writing nuclear reactions. For example, let s consider what happens when uranium-238 undergoes alpha decay. Uranium-238 has 92 protons and 146 neutrons and is symbolized as After it emits an alpha particle, the nucleus now has a mass number of 234 and an atomic number of 90. 

In a closed system, where the numbers of A and B atoms are conserved, a change in any subsystem must affect the rest of the system—atoms must be exchanged internally to accomplish the transformation. For each mole transformed, the change in F for the X B moles of the B component is FB(X B) — FB(XB)]X B, with a similar term for the (1 — X B) moles of the A component,... 

Solution On the left-hand side of the equation we assume that we have a 24Na nuclide (with 11 electrons) and a single positron, which is an antilepton. The conservation rules imply that the mass number of the product will be 24, the atomic number will be Z= 11 + 1, the 11 electrons will carry over, and an antilepton has to be created to conserve lepton number. Thus,... 

The law of conservation of matter states that in a closed system when a chemical change occurs, there is no change in mass. This is because atoms are conserved in a chemical change so atoms must be balanced in a chemical equation. In a balanced equation, coefficients tell the number of reactant and product substances that react and are produced. Subscripts tell the number of atoms of each kind in these substances. When a coefficient is multiplied by a subscript in a substance formula, the number of atoms is determined. Since a mole is an amount of a substance, the coefficients in a chemical equation can stand for the number of moles that react and are produced. 

The numbers and the types of atoms are conserved in chemical reactions, whereas in nuclear reactions this may not be so. 

Atoms are conserved in a chemical reaction so that the number of carbon atoms, oxygen atoms, and hydrogen atoms must be the same on each side of the equation. The formula states that one atom of carbon reacts with one molecule of water to form one molecule of carbon monoxide and one molecule of hydrogen gas. The relative amounts of the substances participating in a reaction are given by the coefficients in the reaction formula, termed stoichiometric coefficients. In this case all the stoichiometric coefficients are one. 

Nuclear transmutations are represented by nuclear equations. Nuclear equations show the change in the nucleus as well as the particle emitted during the decay process. Just like chemical equations, these equations must follow the Law of Conservation of Mass and the Law of Conservation of Charge. That is, they are balanced by equating the sum of mass numbers on both sides of a reaction equation and the sum of atomic numbers on both sides of a reaction equation. 

Beyond atomic spectroscopy muonium renders the possibility to search directly and sensitively for yet unknown interactions between the two charged leptons from two different generations. Among the mysteries observed for leptons are the apparently conserved lepton numbers. As a matter of fact, several distinctively different lepton number conservation schemes appear to hold, some of which are additive and some are multiplicative, parity-like. Some of them distinguish between lepton families and others don t [46,47,48,49,50]. No local gauge invariance has been revealed yet which would be associated with any of these empirically established laws. Since there is common believe [51] that any discrete conserved quantity is connected to a local gauge invariance, a breakdown of lepton number conservation is widely expected, particularly in the framework of many speculative models. 

Note that in equation (10), as in the other nuclear equations listed, atomic numbers and mass numbers are both conserved. This reaction was the first artificial transmutation, carried out (as contrasted to spontaneous transmutations or natural radioactivity in which one nucleus is transformed to another, irrespective of the influence of man). The a particle in equation (10) is the projectile and the nitrogen nucleus the target. 

A beta particle can be represented by the symbol e. The reaction 2349iPa — 23492U + e shows the mass numbers to add up to be the same on both sides of the equation and the atomic numbers (nuclear charges) to add up to be the same on both sides as well. All masses and nuclear charges have been conserved. 

An unbalanced chemical equation is of limited use. Whenever you see an equation, you should ask yourself whether it is balanced. The principle that lies at the heart of the balancing process is that atoms are conserved in a chemical reaction. The same number of each type of atom must be found among the reactants and products. Also, remember that the identities of the reactants and products of a reaction are determined by experimental observation. For example, when liquid ethanol is burned in the presence of sufficient oxygen gas, the products will always be carbon dioxide and water. When the equation for this reaction is balanced, the identities of the reactants and products must not be changed. The formulas of the compounds must never be changed when balancing a chemical equation. That is, the subscripts in a formula cannot be changed, nor can atoms be added or subtracted from a formula. 

Note also that a new element, radon (Rn), is created as a result of the alpha decay of the unstable radium-226 nucleus. The type of equation shown above is known as a nuclear equation because it shows the atomic number and mass number of the particles involved. It is important to note that both mass number and atomic number are conserved in nuclear equations. The accounting of atomic numbers and mass numbers below shows that they are conserved. 

The radioactive decay processes you have just read about are all examples of nuclear reactions. As you probably noticed, nuclear reactions are expressed by balanced nuclear equations just as chemical reactions are expressed by balanced chemical equations. However, in balanced chemical equations, numbers and kinds of atoms are conserved in balanced nuclear equations, mass numbers and atomic numbers are conserved. 

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