Neutron symbol

Proton symbol 1 p Neutron symbol Jn Electron symbol ie... 

Thus, the three isotopes of neon, atomic weights 19.99, 20.99, and 21.99, have the same atomic number (10) but different mass numbers. All the nuclei of neon have 10 protons, but the nuclei of the isotope of mass number 20 have 10 neutrons, those of mass number 21 have 11 neutrons, and those of mass number 22 have 12 neutrons. Symbolically, these nuclei are represented as fJNe, iJNe, wNe. The mass number is the nearest integer to the atomic weight of the isotope. 

The 1 in the lower left of the proton symbol represents 1 proton, and the 0 in the lower left comer of the neutron symbol represents 0 protons. The -1 in the lower left comer of the electron symbol is a bit different from the other atomic numbers, but it will make sense when we see it in (he context of nuclear decay a bit later in this section. 

Nowadays, chemical elements are represented in abbreviated form [2]. Each element has its ovm symbol, which typically consists of the initial upper-case letter of the scientific name and, in most cases, is followed by an additional characteristic lower-case letter. Together with the chemical symbol, additional information can be included such as the total number of protons and neutrons in the nucleus, the atomic number (the number of protons in the nucleus) thus isotopes can be distinguished, e.g., The charge value and, finally, the number of atoms which are present in the molecule can be given (Figure 2-3). For example, dioxygen is represented by O2. 

Atoms with the same number of protons but a different number of neutrons are called isotopes. To identify an isotope we use the symbol E, where E is the element s atomic symbol, Z is the element s atomic number (which is the number of protons), and A is the element s atomic mass number (which is the sum of the number of protons and neutrons). Although isotopes of a given element have the same chemical properties, their nuclear properties are different. The most important difference between isotopes is their stability. The nuclear configuration of a stable isotope remains constant with time. Unstable isotopes, however, spontaneously disintegrate, emitting radioactive particles as they transform into a more stable form. 

Element Symbol Atomic Protons Neutrons Total number Atomic... 

Plutonium (symbol Pu atomic number 93) is not a naturally occurring element. Plutonium is formed in a nuclear reaction from a fertile U-238 atom. Since U-238 is not fissile, it has a tendency to absorb a neutron in a reactor, rather than split apart into smaller fragments. By absorbing the extra neutron, U-238 becomes U-239. Uranium-239 is not very stable, and undergoes spontaneous radioactive decay to produce Pu-239. 

The mass number of an atom, given the symbol A, is found by adding up the number of protons and neutrons in the nucleus ... 

Relate a nuclear symbol to the number of protons and neutrons in the nucleus. 

Selenium is widely sold as a dietary supplement. It is advertised to protect women from breast cancer. Write the nuclear symbol for naturally occurring selenium. It has 34 protons and 46 neutrons. 

Consider the following nuclear symbols. How many protons, neutrons, and electrons does each element have What elements do R T, and X represent ... 

Write the atomic symbol for the element whose ion has a — 2 charge, has 20 more neutrons than electrons, and has a mass number of 126. 

Nuclear symbol Charge Number of protons Number of neutrons Number of electrons g 60... 

A glance at the periodic table will show that the subscripts we have attached to our symbols are the atomic numbers of the elements designated by the symbols—92 for U, 56 for Ba, 36 for Kr. The zero subscript attached to the neutron denotes the lack of charge on this particle. If we look at the subscripts,... 

Actually, then, by our symbol jjU we are representing not an atom, but a nucleus. Our equation is written in terms of nuclei and particles associated with them. This nuclear equation tells us nothing about what compound ol uranium was bombarded with neutrons or what compound of barium is formed. We are summarizing only the nuclear changes. During the nuclear change there is much disruption of other atoms because of the tremendous amounts of energy liberated. We do not know in detail what happens but eventually we return to electrically neutral substances (chemical compounds) and the neutrons are consumed by other nuclei. 

The outstanding characteristic of the actinide elements is that their nuclei decay at a measurable rate into simpler fragments. Let us examine the general problem of nuclear stability. In Chapter 6 we mentioned that nuclei are made up of protons and neutrons, and that each type of nucleus can be described by two numbers its atomic number (the number of protons), and its mass number (the sum of the number of neutrons and protons). A certain type of nucleus is represented by the chemical symbol of the element, with the atomic number written at its lower left and the mass number written at its upper left. Thus the symbol... 

Fig. 12. Interface width a as a function of annealing time x during initial stages of interdiffusion of PS(D)/PS(H) [95]. Data points are obtained by a fit with error function profiles of neutron reflectivity curves as shown in Fig. 11. Different symbols correspond to different samples. The interface width a0 prior to annealing is also indicated (T) and is subtracted quadratically from the data (a = [

Because isotopes of the same element have the same number of protons and the same number of electrons, they have essentially the same chemical and physical properties. However, the mass differences between isotopes of hydrogen are comparable to the masses themselves, leading to noticeable differences in some physical properties and slight variations in some of their chemical properties. Hydrogen has three isotopes (Table B.2). The most common ( H) has no neutrons so its nucleus is a lone proton. The other two isotopes are less common but nevertheless so important in chemistry and nuclear physics that they are given special names and symbols. One isotope (2H) is called deuterium (D) and the other ( H) is called tritium (T). 

Element Symbol Protons Neutrons Electrons number... 

An isotope is usually specified by its mass number. The mass number is the total number of protons and neutrons contained in a nucleus. We can represent any isotope of a chemical element completely by writing its chemical symbol (AT) preceded by a superscript giving its mass number A) and a subscript giving its atomic number (Z) Mass number A... 

A sample of lead atoms is analyzed by mass spectrometry. The bar graph in the margin shows the results. Use information from the graph to write the elemental symbol that represents each Pb isotope and estimate the natural abundance of each. List the number of protons and neutrons for each isotope. 

C02-0047. Write the symbols of the following isotopes (a) Z = 26 with 30 neutrons (b) U (c) argon with two more neutrons than protons and (d) an atom with 9 protons, 10 neutrons, and 9 electrons. 

C02-0077. Write the correct elemental symbols for the following nuclei (include the atomic number subscript) (a) helium with the same number of neutrons and protons (b) tungsten with 110 neutrons (c) the nucleus with Z = 28 and N — 32 and (d) the nucleus with 12 protons and 14 neutrons. 

C02-0092. Except for beiyllium, each of the elements with Z values from 1 to 8 has a stable isotope with the same number of protons as neutrons. Write the correct atomic symbols for each of these isotopes. 

A — Z N. Because protons and neutrons each have molar mass near 1 g/mol, A is always close to the numerical value of the molar mass of that isotope. For example, fluorine has a molar mass of 18.998 g/mol and A — 19. A particular nuclide can be described by its elemental symbol, X, preceded by the value of A as a... 

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