Elements relative weights

Iron is a relatively abundant element in the universe. It is found in the sun and many types of stars in considerable quantity. Its nuclei are very stable. Iron is a principal component of a meteorite class known as siderites and is a minor constituent of the other two meteorite classes. The core of the earth — 2150 miles in radius — is thought to be largely composed of iron with about 10 percent occluded hydrogen. The metal is the fourth most abundant element, by weight that makes up the crust of the earth. 

With the acceptance of Dalton s Atomic Theory, it became necessary to determine the atomic weights of the various elements, i.e., not the absolute atomic weights, but the relative weights of the various atoms with reference to one of them as unit." ... 

Relative weights of the three equivalent changes are given hy the coefficients and an appropriate reduced matrix element determines the magnitude of the perturbation. 

The simplest unit of an element is the atom. The atom is never broken down into smaller particles in chemical reactions. The relative weight of an atom is given by its atomic weight, which appears on the periodic table for each element. An amount of an element equal to its atomic weight in grams is one mole of the element. 

The English chemist John Dalton became one of the most famous scientists of the eighteenth century. Although he was known to the public for one idea, that chemical compounds were formed when the atoms of one element joined with the atoms of another, there was much more than this to Dalton s theory. He revolutionized chemistry by emphasizing that atoms have relative weights and that these relative weights can be measured. 

Perhaps it is worth emphasizing again that the importance of Dalton s theory didn t lie in the assumption that matter is composed of indestructible atoms. That was a very old idea. On the contrary, his idea was significant because it was a theory that explained how chemical compounds are formed and because the idea of atoms with different relative weights made it possible to turn chemistry into a quantitative science. As long as chemists held on to the old idea that elements could combine with one another in a variety of different proportions, they could describe chemical reactions only in a qualitative manner. It was Dalton who changed all this. 

Dalton s theory hardly won immediate acceptance, and debate about it continued for decades. Chemists generally accepted the idea that elements combine in fixed proportions, and they found the idea of relative weights extremely useful. However, many doubted the reality of Dalton s atoms. Atoms, after all, were too small to be seen, and... 

Berzelius s own experiments soon convinced him that Dalton was right to conclude that atoms always combine with one another in small whole-number ratios. Berzelius realized that determining the relative weights of all of the elements would be of enormous value to chemistry, because it would then be possible to determine the exact composition of any chemical compound. Without work of this kind, he said, no day could follow the morning dawn. Because he knew of no other chemist who was pursuing this line of research, he decided to do it himself. 

Dalton had arbitrarily assigned a relative weight of 1 to hydrogen, the lightest element. But Berzelius didn t follow the English chemist s example. Instead he used two different systems at different points in... 

The supposition that changes in the properties of substances are connected with changes in the numbers, movements, and arrangements of different kinds of minute particles, was used in a general way by many naturalists of the 17th and 18th centuries but Dalton was the first to show that the data obtained by the analyses of compounds make it possible to determine the relative weights of the atoms of the elements. 

As a result of his work on relative weights, Dalton formulated the Law of Multiple Proportions, which states that when elements combine to form more than one compound, then the ratio of the masses of elements in the compounds are small whole number ratios of each other. For example, the elements carbon and oxygen form the two compounds carbon monoxide (CO) and carbon dioxide (CO ). The ratio of... 

Atomic Weight The mass of an element relative to its atoms. 

Atom is the smallest unit of mass of an element that can participate in chemical changes. The relative weights of atoms of different elements are known as atomic weights. The atoms of the same element do not necessarily... 

Convinced that elements did not react in a random fashion, that somehow their properties and behavior were systematic, Mendeleev wrote the names of the known elements on cards. Then he listed their various properties and the relative weights of their atoms. These atomic weights were a hot topic. They... 

In 1799 Joseph Proust (1754-1826), a French chemist, observed that specific compounds always contained the same elements in the same ratio by mass. This came to be known as the law of definite proportions. The law of definite proportions provided a means for determining relative weights for numerous atoms and verified John Dalton s theory that elements are made up of atoms. Dalton (1766-1844) was an English teacher, chemist, and physicist. He used modern scientific methodology to develop long-lasting atomic theories. 

Explain what a mole is in terms of the relative weight of an element. 

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