Mixtures, elements, solutions and compounds. Wan Wei Ren. What are elements?. The most fundamental substances from which all material things are constructed. The smallest particle that retains the properties of an element is an atom
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In the periodic table of the elements, elements are arranged in a series of rows so that those with similar properties appear in vertical columns.
Elements of the same period have the same number of electron shells; with each group across a period, the elements have one more proton and electron and become less metallic. This arrangement reflects the periodic recurrence of similar properties as the atomic number increases.
Period 4 includes the biologically essential elements potassium and calcium, and is the first period in the d-block with the lighter transition metals. These include iron, the heaviest element forged in main-sequence stars and a principal component of the earth, as well as other important metals such as cobalt, nickel, copper, and zinc. Almost all have biological roles.
Period 5 includes the important metals silver and tin and the biologically important element iodine.
Period 6 is the first period to include the F block, with the lanthanides (rare earth elements), and includes the heaviest stable elements. Many of these heavy metals are toxic and some are radioactive, but platinum and gold are largely inert.
All elements of period 7 are radioactive. This period contains the heaviest element which occurs naturally on earth, uranium. Most of the subsequent elements in the period have been synthesized artificially. Whilst some of these (e.g. plutonium) are now available in tonne quantities, most are extremely rare, having only been prepared in microgram amounts or less. Some of the later elements have only ever been identified in laboratories in quantities of a few atoms at a time.
Elements in a group have similar configurations of the outermost electron shells of their atoms: as most chemical properties are dominated by the orbital location of the outermost electron. There are three conventional ways of numbering: One using Arabic numerals, and two using Roman numerals.
Compounds can be separated into simpler substances by chemical reactions.
Water can be broken down into hydrogen and oxygen by passing an electric current through it (Electrolysis) .
Electrolysis is a method of using an electric current to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially highly important as a stage in the separation of elements from naturally-occurring sources such as ores using an electrolytic cell.