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Chemistry is the scientific study of the properties and behavior of matter. [1] It is a physical science within the natural sciences that studies the chemical elements that make up matter and compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during reactions with other substances.
The protoscience of chemistry, and alchemy, was unsuccessful in explaining the nature of matter and its transformations. However, by performing experiments and recording the results, alchemists set the stage for modern chemistry. The history of chemistry is intertwined with the history of thermodynamics, especially through the work of Willard ...
A chemical bond is an attraction between atoms. This attraction may be seen as the result of different behaviors of the outermost or valence electrons of atoms. These behaviors merge into each other seamlessly in various circumstances, so that there is no clear line to be drawn between them.
English chemist John Daniell (left) and physicist Michael Faraday (right), both credited as founders of electrochemistry.. Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference and identifiable chemical change.
Access to the structure provided answers to central questions in biology, regarding the movement of ions across the cell membrane. In particular, the structure revealed the mechanism with by which these channels move potassium ions both quickly and selectively, reliably preventing similarly sized sodium ions from passing through.
By 1829, Döbereiner had found other groups of three elements (hence "triads") whose physical properties were similarly related. [2] He also noted that some quantifiable properties of elements (e.g. atomic weight and density) in a triad followed a trend whereby the value of the middle element in the triad would be exactly or nearly predicted by taking the arithmetic mean of values for that ...
The Lindemann criterion states that melting occurs because of "vibrational instability", e.g. crystals melt; when the average amplitude of thermal vibrations of atoms is relatively high compared with interatomic distances, e.g. <δu 2 > 1/2 > δ L R s, where δu is the atomic displacement, the Lindemann parameter δ L ≈ 0.20...0.25 and R s is ...
The mole is widely used in chemistry as a convenient way to express amounts of reactants and amounts of products of chemical reactions. For example, the chemical equation 2 H 2 + O 2 → 2 H 2 O can be interpreted to mean that for each 2 mol molecular hydrogen (H 2 ) and 1 mol molecular oxygen (O 2 ) that react, 2 mol of water (H 2 O) form.