Element symbols isotope specification

As noted in Section 2.3, we often do not explicitly write the atomic number of an isotope because the element symbol is specific to the atomic number. In studying nuclear chemistry, however, it is often useful to include the atomic number in order to help us keep track of changes in the nuclei. 

CARBON. (CAS 7440-44-0], Chemical element symbol C. at. no. 6. at. wl. 12.011. periodic table group 14. mp 3.550°C (approximate), bp 4,2893C (approximate), density 3.52 g/cm (diamond at 20 C). 2.25 g/cmJ (graphile at 20 C). The specific gravity of amorphous carbon at 20 C ranges from 1,8 to 2.1, There are two stable isotopes of the element. i C and l3C. and Tour known radioactive isolopes, l0C. "C. IJC, and l5C. Because the half-life laboul 5,760 years) of HC has been established, this isotope is useful for dating ancient documents and materials. 

Because the variables in these equations often need multiple indexing (e.g. element, isotope and source) the amount of indexing can be reduced by using italic element symbols to refer to the specific radioactivity, or concentration, of that nuclide in the sample e.g. 

Most elements in their natural state are made up of more than one kind of atom. These different kinds of atoms of a specific element are called isotopes and differ from one another only in the number of neutrons in their nuclei. A symbol incorporating atomic number, mass number, and elemental symbol is used to represent specific isotopes. Objective 3, Exercises 2.16 and 2.22... 

Free atoms prefer to exist in the neutral (zero charge) state. This results when the number of protons equals the number of electrons within the atom. Note Protons have a unit charge of+1, whereas electrons have a unit charge of -1 (neutrons have no charge). The number of protons within the nucleus of an atom is described by the atom s atomic number (Z). This number appears in the periodic table above the elements symbol (see Appendix A.l). The sum of protons and neutrons within the nucleus of a specific atom, or more specifically, that for a specific isotope of an element is defined by the atomic mass number (A), which is also referred to as the mass number. 

Most nuclear reactions involve the breaking apart of the nucleus into two or more different elements or subatomic particles. If we know all but one of the particles, then the unknown particle can be determined by balancing the nuclear equation. When chemical equations are balanced, we add coefficients to ensure that there are the same number of each type of atom on both the left and right of the reaction arrow. However, in order to balance nuclear equations we ensure that there is the same sum of both mass numbers and atomic numbers on the left and right of the reaction arrow. Recall that we can represent a specific isotope of an element by the following symbolization ... 

Since the atom itself is neutral, the number of electrons must equal the number of protons. However, the number of neutrons in an atom may vary. Atoms of the same element (same number of protons) that have differing numbers of neutrons are called isotopes. A specific isotope of an element can be represented by the following symbolization ... 

Note that of all the isotopes of all the elements, only those of hydrogen, and H, also have specific atomic symbols, D and T, with associated names deuterium and tritium. 

The atoms of all isotopes of any specific element have the same number of protons. This number is called the atomic number, Z, and is a characteristic of the element. The nuclei of different isotopes differ in the number of neutrons providing for a different number of nucleons in the nuclei. One way of referring to specific isotopes is to provide the total number of nucleons, A, which is the mass number. Atoms of the different isotopic forms of an element, the nuclides, are distinguished by using the mass number as a superscript to the left of the element s symbol. So, the nitrogen isotope containing 8 neutrons will have a mass number of 15 and is represented by 15N (or N-15). Working from the other direction, we can determine the number of neutrons in an isotope by... 

Elements are described as atoms possessing the same number of protons. However, not all atoms of an element possess the same number of neutrons. These different varieties of an element that contain the same number of protons but different numbers of neutrons are known as isotopes. Isotopes will possess the same chemical properties, since they are determined by the number of electrons and protons, but they will have a different mass. In Chapter 5, we will look at how the number of neutrons affects the stability of the nucleus. All atoms of a specific isotope are known as nuclides. Isotopes are represented using a variety of symbols. Three of these are shown in Table 4.2. 

Chemists and physicists use specific symbols to depict these mass and charge relationships. For any atom X, superscript values denote the nuclear mass of the atom (number of protons plus neutrons), whereas subscript values denote the atom s atomic number (number of protons). Thus l2,C, 1gC, and 14C are three different isotopic forms of the element carbon. In this convention, the letters define... 

A radioactive isotope s half-life (symbol t) is the time required for the concentration of the nuclei in a given sample to decrease to half its initial concentration. The half-life is specific to a radioactive element and varies widely (from three hours for Sr-87 to millions of years for U-238, for example). The mathematical expression for half-life is as follows (k is the rate constant) ... 

Our journey into the center of the atom begins with a brief review. You learned in Chapter 2 that the protons and neutrons in each atom are found in a tiny, central nucleus that measures about 1/100,000 the diameter of the atom itself You also learned that the atoms of each element are not necessarily identical they can differ with respect to the number of neutrons in their nuclei. When an element has two or more species of atoms, each with the same number of protons but a different number of neutrons, the different species are called isotopes. Different isotopes of the same element have the same atomic number, but they have a different mass number, which is the sum of the numbers of protons and neutrons in the nucleus. In the context of nuclear science, protons and neutrons are called nucleons, because they reside in the nucleus. The atom s mass number is often called the nucleon number, and a particular type of nucleus, characterized by a specific atomic number and nucleon number, is called a nuclide. Nuclides are represented in chemical notation by a subscript atomic number (Z) and superscript nucleon number (A) on the left side of the element s symbol (X) ... 

This symbol is equivalent to writing fluorine-19. This alternative representation is frequently used to denote specific isotopes of elements. 

All elements with more than 83 protons are radioactive. The symbol for isotopes (Chap. 2) consists of the element s symbol with a subscript denoting the atomic number, and a superscript denoting the atomic mass which is the sum of protons and neutrons. Another method for denoting a specific isotope is to write the name of the element with a hyphen followed by the nuclear mass. The atomic number is implied by the element s name. 

What are isotopes To what do the atomic number and the mass number of an isotope refer How are specific isotopes indicated symbolically (give an example and explain) Do the isotopes of a given element have the same chemical and physical properties Explain. 

In referring to a specific isotope, use the symbolism Sy, where Sy is the symbol for the element, A is the mass number (sum of the number of protons and neutrons) of the isotope, and Z is the atomic number (number of protons) of the element. 

The three isotopes of hydrogen are represented as follows using this notation Jh, jH, and iH. When these symbols are not convenient to use, as in written or spoken references to the isotopes, the elemental name followed by the mass number is used. Thus, the three hydrogen isotopes are hydrogen-1, hydrogen-2, and hydrogen-3. These three isotopes have specific names protium (A = 1), deuterium (A = 2), and tritium (A = 3). 

Isotopes of elements that emit nuclear radiation are called radioisotopes. In nuclear reactions, a specific isotope of an element may behave differently from another isotope of the same element. Thus, all particles involved in nuclear reactions are designated by a symbol, a mass number (the sum of protons and neutrons in the particle), and an atomic nmnber (or charge for electrons or positrons). The symbolism used was introduced in Section 2.3. It is zX, where X is the symbol for the particle, A is the mass number, and Z is the atomic number or charge. When X represents the nucleus of an isotope of an element, the chemical symbol for the element is generally used. 

Figure 3.4 gives the names, symbols, and compositions of the isotopes of hydrogen and helium. Nuclide is a general term for a specific isotope of an element. 

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