View source for Atomic masses of elements 104 and higher are approximations

Every material is composed of a great number of atoms. The type and number of atoms determines the physical and chemical characteristics of that material. A compound, a combination made up of a number of different atoms, is called a molecule. Chemistry is the study of combinations of atoms, and especially, of molecules. With the help of already gained knowledge, chemists attempt to produce synthetic materials, which may work better than the materials that are being used at the present time.

Chemistry is able to transform raw materials into new materials and compounds with different and new characteristics, products which can often be used for a variety of new purposes. A few examples of what has been produced in the chemical industry: Varnishes and sprays, paints, plastics, cosmetics, medicines and cleaning products or even modern materials for the textile industry. Metals and alloyed steel are also produced in their present form thanks to the reactions and processes of industrial chemistry.

Another very important example of the uses of chemistry is the production of pure materials for various uses. For example, integrated circuits and photo cells can be produced from highly purified silicon. Chemistry is also gaining importance in environmental matters. Industrial processes which produce various materials, as well as simple consumption of raw materials, can cause harmful pollutants to be released into the atmosphere. With the help of special, highly developed processes, chemistry can transform those harmful pollutants into less dangerous materials. These materials, which are no longer useful to heavy industry, can then be returned to their natural place in nature. Or, they can be recycled. With the help of advances in chemistry, more and more useful materials are manufactured for day-to-day life. At the same time, our environment is protected by the removal of some of the more harmful byproducts of chemical reactions in heavy industry.

Characteristics of Materials

Our environment is composed of innumerable objects, things in combination with one another, depending on one another. Physics would call them objects, or bodies. Biology would classify those that are living as organisms, or living matter. Chemistry concentrates on the composition of matter. In order to safely distinguish and differentiate one object from another, the characteristics of both must be well known. So in chemistry, all materials have their own original and distinguishable, identifiable criteria. Some characteristics are able to be distinguished from others using our senses. To distinguish others, it is necessary to carry out more thorough chemical and physical analyzes.

The characteristics of materials can be determined by human sense organs, like sight. The colour of an object, or its texture, or its crystalline shape, or other shape, can be seen. Taste and odour can also be used to determine the nature of an object. Of course, it should be mentioned that professional chemists have long given up on senses like taste and smell, citing safety concerns.

Periodic Table of the Elements, Chemical Symbols

Atoms of various elements differ in the number of individual particles they contain (neutrons, protons and electrons). These three are the constituent particles which atoms are made of.

The periodic table of the elements contains the elements in systematic relation to one another. Their order is determined by the amount of protons each contains, and at the same time the amount of electrons each element contains in its electron cloud. 
The amount of protons of an element in the periodic table is seen as its defining factor, its atomic number.

Vertically, the periodic table is arranged in groups. Elements in the same group have the same number of electrons in their outermost shell. There are eight main groups of elements, denoted with the Roman numerals from I to VIIII. Some groups are better known by their familiar names. The number of electrons in an element's most outer shell increases from left to right across the periodic table. Group I is called alkaline metals. Group II is called alkaline earth metals. Elements of Group VII are called halogens, with Group VIII the noble gases.

Besides these eight groups, there are other groups whose elements differ from Groups I-VIIIA. These groups' characteristics are so different that they are denoted with Roman numerals plus the letter B at the end: IB-VIIIB. These are the transition metals.

Elements of the first main group have one electron in their outer shells. Elements in the second group have two, and so forth, up to Group VIIIA (the noble gases), which have eight electrons in their outer orbital. Eight electrons, for A Group elements, means a full electron shell, at which time another more outer electron shell begins to fill.

Using more simplified atomic models, one of the basic concepts is that individual elements try to fill their outer shells completely. This basic characteristic of elements can help us to understand why chemical reactions take place. As long as elements in the main groups do not have full outer shells, that is, that they have a small amount of electrons, they will try to donate those electrons to other groups (elements from Groups I through IV). If, on the other hand, elements have nearly full shells, that is, a lot of electrons, and they are lacking only one or a few electrons to complete their outer shell, they will try to attract electrons (elements in Groups V-VII). Because elements in Group VIII (the noble gases) already have filled outer shells, they do not enter into reactions with other elements. They are said to be unreactive, or inert.

In addition to vertical groups, elements in the periodic table are arranged horizontally, from left to right - in so-called periods. The difference between periods is found in the number of electron shells (from up to down in the table, the number of outer shells increases by one from one period to the next). In the first period, elements (hydrogen (H) and helium (He)) have only one shell. Elements in the second period have two shells, and so on. Various characteristics of the individual elements are more predictable thanks to their placement in the periodic table. In addition, colours are used to make the elements even more noticeable.

Hydrogen is given a white colour, because it cannot be placed in the same category with any other element.

The first column (Group IA) is called the alkaline metals and is given the color yellow.

The second column (Group IIA) is called the alkaline earth metals and are purple.

The transition metals are dark yellow, and they belong to other groups, B groups.

In addition, lanthanoids and actinoids (brown and pink) are part of these other B groups.

In groups IIIA-VIA, a number of metals are found. These are emphasized with light blue.

Light green is the colour given metalloids, in the same groups as some other metals.

Non-metals are dark-green and can be found in Groups IVA to VIIA.

The noble gases, in Group VIIIA have been given a dark blue colour. 
Besides non-metals, metalloids and rare metals, all other elements are considered to be metallic, or metals.

Meaning of some of the abbreviations given chemical symbols of elements in the periodic table: 
The top number in coloured letters in the period table is the atomic number, also an indication of the amount of proteins in the nucleus.

Abbreviations (for example H,Cl,Fe) are chemical symbols of elements, often, but not always, shortened from their names (Hydrogen, Chlorine, Iron).

The number at the bottom of the box for each element indicates that element's relative atomic mass (number of protons plus number of neutrons in the nucleus, together).

Further information:

- Atomic masses of elements 104 and higher are approximations.

- The names of elements 101-109 were internationally recognized August 30, 1997.

- Uranium, with atomic number 92, is the heaviest naturally-occurring element. Elements with higher atomic numbers are so unstable that they are not found to exist in nature. They are therefore synthesised in the laboratory.

- Lanthanoids and actinoids are separated from the main body of the periodic table to save space, because the sixth and seventh periods each have 32 elements.





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