Positive thinking 90-92, Table

About 100 different kinds of atoms make up all kinds of matter, and they are classified in a table—the Periodic Table of Elements—according to their construction. The center of any atom is a nucleus containing protons and neutrons. The protons have a positive charge and the neutrons are neutral so the nucleus is positively charged. Electrons, equal in number but opposite in charge to the protons, move around the nucleus in orbits. You might think of an atom like a solar system. The nucleus acts like the sun the electrons orbit the nucleus like the planets circle the sun. 

Thinking about the position of elements in the periodic table and their valence electron structure should help in understanding the relative order of the reduction potentials. Fluorine gas is very electronegative and readily accepts electrons to obtain a stable configuration. Conversely, alkalines and... 

This which I have said against the tables of affinity in general naturally applies to the one I am presenting, but I think, nevertheless, that it may have some utility at least in so far as the more numerous experiences and the applications of calculation to chemistry place us in position to carry forward our views. Perhaps some day the precision of the data will lead to the point that the mathematician will be able to calculate in his study the phenomena of any chemical combination whatsoever, in the same manner, so to say, as he calculates the movement of the celestial bodies. ... 

Hydrogen is a very special case also when it is a part of other molecules. We saw that in the lithium row and in the sodium row of the periodic table both a valence s state and a valence p state are present. We will see that when these atoms form molecules, the bond orbitals are mixtures of both s and p orbitals. There is no valence p state in hydrogen, and its behavior is quite different. In many ways the hydrogen proton may be regarded as a loose positive charge that keeps a molecule neutral rather than as an atom that forms a bond in the same sense that heavier atoms do. Thus we can think of methane, CH4, as neon with four protons split off from the nucleus, just as we can think of H2 as helium with a split nucleus. 

In your study of chemistry you should make a continual effort to correlate the descriptive facts with the system of chemical theory. For example, the facts about the element phosphorus and its compounds may be more easily remembered if, while studying them, you think about their possible explanation in terms of atomic and molecular structure and also about the way in which they differ from the corresponding facts about other elements, especially in relation to the position of the elements in the Periodic Table, as described in Chapter 5. 

Several traits of atoms are said to have periodic trends , meaning that different atoms in a period have identifiable relationships to one another based on their position. Is that confusing Think of the periodic table as a group picture, maybe of a very large basketball team. Each period is a row of players in the picture, and the "photographer has decided to arrange the players by their characteristics. Of course, no conscious effort was made to arrange the periodic table by any characteristic other than number of protons, but some properties are consistent in its layout anyways. 

Helium, with atomic number 2 and two electrons, is the next element after hydrogen in the periodic table. Both of helium s electrons are in the Ir orbital. This allows them to be as close to the positive charge of the nucleus as possible. Even though the two electron charge clouds occupy the same space, the two electrons are not identical. The property in which they differ is called electron spin. Although the true nature of electron spin is uncertain, it is useful to think of it as if elearons can spin on their axis. We can visualize the two electrons in a helium atom as spinning in opposite directions (Figure 11.13). 

The central tenet of Berzelius world view was the dualistic theory that still pervades our understanding of chemistry—particularly for ionic compounds such as sodium chloride. Briefly, table salt is composed of a positive part (Na ) and a negative part (Cl ). Such dualism was already part of Lavoisier s thinking some 30 years earlierd... 

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