What Elements Are Made of

Qne of the strangest things about Mendeleyev s discovery of the periodic table is that he did not really know why the table was periodic. He did not understand what elements really are in the way that scientists understand them now. Yet he was able to write out a correct periodic table that allowed him to make amazing predictions about unknown elements. He found an idea that worked, but he did not know why it worked. 

we know that elements fit into a periodic pattern because they are made of atoms, just as Democritus suspected. An atom is the smallest particle of an element that still has all the properties of that element. In other words, an atom of gold is no different from a bar of gold except that the atom is much smaller. 

Democritus was wrong when he said that atoms could not be divided into smaller pieces. Atoms themselves are made of three 

An element can be defined by the number of protons in its atoms. All hydrogen atoms have only one proton, whereas all iron atoms have 26 protons and all gold atoms have 47 protons. The number of neutrons can vary, and there are usually more neutrons than protons in elements heavier than aluminum. Atoms of the same element that have different atomic weights due to different numbers of neutrons in the nucleus are called isotopes. Most of the weight of an atom comes from its protons and neutrons. Protons and neutrons have nearly the same mass, or to put it another way, they contain nearly the same amounts of matter. A proton has almost 2,000 times more mass than an electron. 

When Mendeleyev first arranged his periodic table, he put the known elements in order of atomic weight. In the modern table, elements are arranged instead by atomic number—the number of 

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Attention — this is not a textbook It is also not meant to replace one. Nevertheless, there is a lot to be learnt, albeit in a different manner from that in which chemistry is normally presented. The initial question is old and simple "What does the world consist of " This leads to the next question "Who were the researchers who discovered this " They should not be forgotten by us, who take almost for granted all the advantages of progress. After all, the discovery of the 92 elements that occur in the universe and that can also be found on Earth is one of the greatest accomplishments of human intellectual curiosity. Through these discoveries we know what stars are made of, we know the composition of the Earth, and we know which elements are essential for life. 

So the Jabirian system embraced the four classical elements and then buried them, just as the Aristotelian elements allowed but ignored the universalhyle. It marks the beginning of a tendency to pay lip service to Aristotle while getting on with more practical concerns about what things are made of. 

Elements are made of tiny particles called atoms. Although Dalton didn t know what atoms were like, he nevertheless felt that they were necessary to explain why there were so many different elements. 

Abbgy, Theodore S. Elements and the Periodic Table What Things Are Made Of. Quincy, IL Mark Twain Media, 2001. 

Bob nods. Mr. Plex, today I want to tell you how we find out what stars are made of. It is amazing that we know about the elements in stars even though they... 

There are about 91 different elements in nature, and consequently about 91 different kinds of atoms. In addition, scientists have succeeded in making about 20 syn-thehc elements (not found in nature). In this chapter, we examine atoms what they are made of, how they differ from one another, and how they are structured. We also examine the elements that atoms compose and some of the properties of those elements. 

A simple answer to this question is All substances are made of elements . Then, what are elements The ancient Greeks and Indians tried to find an answer to this question. 

Most metals are made of atoms that have an outer configuration of s2, which we would expect to completely fill the band of m.o. s we have described. With the band completely filled and no empty levels above, we would not expect elements such as beryllium to be metallic. What happens is that the empty p orbitals also split into a band. Although the energy of the 2p orbital of an isolated Be atom is about 160 kJ greater than that of the 2s orbital, the bottom part of the 2p band overlaps the upper part of the 2s band, yielding a continuous conduction band that has plenty of unoccupied orbitals. It is only when these bands become filled with 2p electrons that the elements lose their metallic character. 

Chemists have agreed on a sort of scientific shorthand in which letters stand for the names of elements, substances composed of only one kind of atom. They call these letters chemical symbols. Combinations of symbols represent the different atoms in a particular kind of molecule. These combinations are called formulas, and they show what elements are contained in a compound. A compound, as you can probably tell, is a substance made up of molecules... 

Real-World Question What percentages of common household substances are made of the element carbon 2. Calculate the percent composition of the element carbon in the molecules of each substance. Use the formula method outlined in the textbook to calculate your... 

It s time to clean out your room—again. Where do all these things come from Some are made of cloth and some of wood. The books are made of paper and an endless array of things are made of plastic. Fewer than 100 different kinds of naturally occurring elements are found on Earth. They combine to make all these different substances. What makes elements form chemical bonds with other elements The answer is in their electrons. 

Enzymes, hormones, and what I call special proteins are very important in how they influence our body chemistry, which is why I ve devoted a chapter to them. The reason they are so significant is that dietary deficiencies of any chemical elements needed by them usually have a drastic impact on health, tending to do more harm to our bodies in a shorter period of time than deficiency effects on any other body parts. All three are made of the chemical elements I ve discussed in previous... 

Dalton s atomic theory gave chemists a model of the particle nature of matter. However, it also raised new questions. If all elements are made up of atoms, why are there so many different elements What makes one atom different from another atom Experiments in the late 19th century began to suggest that atoms are made up of even smaller particles. Present-day chemistry explains the properties and behavior of substances in terms of three of these smaller particles. You will learn more about each of these particles in Section 2.2. 

The substance to be identified must be in a pure condition in order that its physical properties may be accurately determined and the conclusions drawn from its reactions may be trustworthy. If the substance does not show the characteristics of a pure compound, it must be purified by the methods already outlined (7, 8). A qualitative analysis is next made to determine what elements are present. The action of the compound is then studied with water, concentrated sulphuric acid, a hot and a cold solution of sodium hydroxide, dilute hydrochloric acid, acetyl chloride, bromine, sodium carbonate, phenylhydrazine, and Schiff s reagent. The carbohydrate test (386) should be applied, and if the compound contains sulphur the reactions given above under sulphur compounds should be studied. It is sometimes advisable and is often necessary to use other reactions than those just mentioned. A few examples will now be given. 

Coins One of the transition groups is often called the coinage group because at one time many coins are made of these metals. Which group is this What elements in this group is still used in many U.S. coins today ... 

The postulates also account for the law of definite proportions. Com-poimds are made of elements in fixed or definite proportions. Since the atoms have fixed mass, compounds should have elements in a fixed ratio with respect to mass. Finally, these postulates predict what is known as the law of multiple proportions. According to this law, if two elements form two or more different compounds, the ratio of the mass of one element of these compounds to a fixed mass of the other element is a simple whole number. 

What elements are stars other than the Sun made of ... 

Scientists say that matter is anything that "has mass and occupies space." Matter is the "stuff" of which everything is made. It can be classified and subdivided in many ways, depending on what we are trying to demonstrate. All the types of matter we have studied are made of atoms. They differ in whether these atoms are all of one element, or are of more than one element, and also in whether these atoms are in physical mixtures or chemical combinations. 

For the most part, organometallic ligands are made of either carbon or nitrogen. These two elements serve as excellent guides for what you can expect when using ligands. In this section, we describe how the atoms function as ligands, and we also describe boron, which behaves in a unique manner. 

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