Chemical elements
In chemistry, an element is a type of atom. All matter around us (solids, liquids, and gases) are made up of atoms. In nature there are 94 different types of atoms—elements. Some elements are very abundant. For instance water is made up of the elements hydrogen and oxygen and, obviously, there is much water in the oceans. Carbon is an important part of most living creatures as well as of fossile fuels, which are the remains of plant material that once lived. Other elements (atoms) are rare on earth, such as the noble gas neon. Some elements are stable (live for ever), while some elements have finite life times and decay to other elements, while sending out radiation (these are the so-called radioactive elements). A well-known radioactive element is plutonium. About 20 elements are man-made, they are characterized by having very short life times and being radioactive.
We recall that an atom consists of a positive nucleus of charge eZ, where e is the elementary charge, and the integral number Z is the atomic number. Remember that Z electrons (of charge −e) "orbit" the nucleus, so that an atom is neutral. The elements are distinguished by their value of Z. For instance, the elements just mentioned have the Z-value in brackets: hydrogen(1), oxygen(8), carbon(6), neon(10), plutonium(94). The naturally occurring elements have Z-values from 1 to 94 (with plutonium being extremely rare in nature and mainly man-made). The man-made elements run from Z = 95 to 118, with holes in between. The names of the elements are of historical origin and may vary between languages, the atomic number Z is a unique and universal label of an element.
| Actinium - Curium | Darmstadtium - Iron | Krypton - Nobelium | Palladium - Sulfur |
|---|---|---|---|
| Actinium - Arsenic | Darmstadtium - Europium | Krypton - Lutetium | Palladium- Protactinium |
| Barium - Bromine | Fermium - Gold | Magnesium - Molybdenum | Radium - Rutherfordium |
| Cadmium - Curium | Hafnium - Iron | Neodymium - Oxygen | Samarium - Sulfur |
| All Elements Sorted Alphabetically (Tantalum - Zirconium) | |||
| Tantalum - Tungsten | Uranium - Zirconium | ||
Overview
Also see List of elements by name