Properties of the Chemical Elements

Among the non-metals, nitrogen and chlorine, for example, are gases, but phosphorus, which resembles nitrogen chemically, is a solid, as is iodine which chemically resembles chlorine. Clearly we have to consider the physical and chemical properties of the elements and their compounds if we are to establish a meaningful classification. 

The chemical properties of the elements in a given group of the Periodic Table change with increasing atomic number. 

General similarities and trends in the chemical properties of the elements had been noticed increasingly since the end of the eighteenth century and predated the observation of periodic variations in physical properties which were not noted until about 1868. However, it is more convenient to invert this order and to look at trends in atomic and physical properties first. 

Other periodic trends which occur in the chemical properties of the elements and which are discussed in more detail throughout later chapters are ... 

Polonium, because of its very low abundance and very short half-life, is not obtained from natural sources. Virtually all our knowledge of the physical and chemical properties of the element come from studies on Po which is best made by neutron irradiation of in a nuclear reactor ... 

The periodic table is one of the most notable achievements in chemistry because it helps to organize what would otherwise be a bewildering array of properties of the elements. However, the fact that its structure corresponds to the electronic structure of atoms was unknown to its discoverers. The periodic table was developed solely from a consideration of physical and chemical properties of the elements. 

The incompletely filled d-subshell is responsible for the wide range of colors shown by compounds of the d-block elements. Furthermore, many d-metal compounds are paramagnetic (see Box 3.2). One of the challenges that we face in this chapter is to build a model of bonding that accounts for color and magnetism in a unified way. First, though, we consider the physical and chemical properties of the elements themselves. 

The physical and chemical properties of the elements show regular periodic trends that can be explained using electron configurations and nuclear charges. We focus on the physical properties of the elements in this section. A preliminary discussion of the chemical properties of some of the elements appears in Section Other chemical properties are discussed after we introduce the principles of chemical bonding in Chapters 9 and 10. 

The smallest unit having the chemical properties of the element are the atoms. All atoms are made up from a number of elementary particles known as the protons, neutrons, and electrons. The protons and neutrons make up an atomic nucleus at the center of the atom, while the electrons, distributed in electron shells, surround the atomic nucleus. The atoms of each element are identical to each other but differ from those of other elements in atomic number (the number of protons in the atomic nucleus) and atomic weight (their weighted average mass) as listed in the table below. 

The number of protons in the nucleus determines the chemical properties of the element. That number is called the atomic number of the element. Each element has a different atomic number. An element may be identified by giving its name or its atomic number. Atomic numbers may be specified by use of a subscript before the symbol of the element. For example, carbon may be designated 6C. The subscript is really unnecessary, since all carbon atoms have atomic number 6, but it is sometimes useful to include it. Atomic numbers are listed in the periodic table and in Table 3-1. 

There were students and researchers in Rutherford s laboratory who knew a good bit of chemistry. Bohr remarked that he was particularly helped at Manchester in his thinking about the physical and chemical properties of the elements by Hevesy, who "distinguished himself among the Manchester group... 

The Structure of the Atom and the Physical and Chemical Properties of the Elements." The Theory of Spectra and Atomic Constitution. Cambridge 1922. Pp. 61126. 

Illustrate the trends associated with several atomic and chemical properties of the elements. 

Chemical reactions take place when the reacting atoms, molecules or ions collide with each other. Therefore the outer electrons are Involved when different substances react together and we need to understand the electronic structure of atoms to explain the chemical properties of the elements. Much of the information about the electronic structure of atoms and molecules is obtained using spectroscopic techniques based on different types of electromagnetic radiation. 

The theory that electrons travel in discrete orbits around the atom s nucleus, with the chemical properties of the element being largely determined by the number of electrons in the outer orbits. The idea that an electron could drop from a higher-energy orbit to a lower one, emitting a photon. 

J. Barrett, Atomic Structure and Periodicity, Royal Society of Chemistry, Cambridge, 2001. This book is meant to act as preliminary reading for the present text, but covers the subject matter in a largely non-mathematical way. The theoretical basis of the Periodic Table is dealt with in considerable detail and is followed by discussions of the periodicities of the main physical and chemical properties of the elements. 

R. J. Puddephatt and P. K. Monaghan, The Periodic Table of the Elements, 2nd edn., Oxford University Press, Oxford, 1986. A concise description of the structure of the Periodic Table and a discussion of periodic trends of many physical and chemical properties of the elements. 

D. M. P. Mingos, Essential Trends in Inorganic Chemistry, Oxford University Press, Oxford, 1998. A new look at trends in physical and chemical properties of the elements and their compounds. This is a general text that would cover the material of most university courses in inorganic chemistry apart from some specialized topics, but is recommended here for the sections on atomic and molecular structure. 

When the elements are ejected from the stars where they were produced, they are in the gas phase. Subsequently, they combine in various chemical compounds and most condense as solids. The nature of those compounds and their behavior in the various environments encountered on their way to becoming part of the solar system can, in principle, be determined from the basic chemical properties of the elements. Evaporation and condensation are also important in the solar system and have played a defining role in determining the properties of planets, moons, asteroids, and the meteorites derived from them, comets, dust... 

The most obvious correlation of the electronegativity scale with the general chemical properties of the elements bears on their division into metals and nonmetals. It is seen that the value x = 2 represents ap-... 

Jhe distribution of beryllium, boron, titanium, vanadium, chromium, cobalt, nickel, copper, zinc, gallium, germanium, tin, molybdenum, yttrium, and lanthanum in the principal coal-producing beds of the Interior Province has been studied by the U. S. Geological Survey. Data, methods of sampling, and analyses are discussed by Zubovic and others (II, 12). This chapter discusses the occurrence of 13 of these elements with respect to geological and geochemical environments of coal deposition and chemical properties of the elements. Zinc and tin are not included in this study because they were detected in only a few samples. 

PERIODIC LAW. Originally stated in recognition of an empirical periodic variation of physical and chemical properties of the elements with atomic weight, this law is now understood to he based fundamentally on atomic number and atomic structure. A modern statement is the electronic configurations of the atoms of the elements vary periodically with their atomic number. Consequently, all properties of the elements that depend on their atomic structure (electronic configuration) tend also to change with increasing atomic number in a periodic manner. 

Since the X-ray spectral lines come from the inner electrons of the atoms, die lines are not related to the chemical properties of the elements or to the compounds in which they may reside. Because the characteristics of die X-ray spectra are associated with energies released through transitions of electrons within the inner shells of the atom, the spectra are simple. Most practical X-ray fluorescence analysis involves the detection of radiation release through electron transitions from outer shells to the K shell (K spectra), outer shells to die L shell (L spectra) and, in very few cases, from outer shells to the M shell (M spectra). 

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