![]() ![]() Some molecules contain one or more unpaired electrons, creating radicals. Charged polyatomic collections residing in solids (for example, common sulfate or nitrate ions) are generally not considered "molecules" in chemistry. However, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well-separated form, such as a directed beam in a vacuum in a mass spectrometer. ![]() When this rule is broken, giving the "molecule" a charge, the result is sometimes named a molecular ion or a polyatomic ion. Thus, molecules exist as electrically neutral units, unlike ions. Molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. However, this definition only works well for substances that are composed of molecules, which is not true of many substances (see below). Several concepts are essential for the study of chemistry some of them are: MatterĪ ball-and-stick representation of the caffeine molecule (C 8H 10N 4O 2)Ī molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. Most chemists specialize in one or more sub-disciplines. Scientists engaged in chemical research are known as chemists. They can be analyzed using the tools of chemical analysis, e.g. Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions. (When the number of atoms on either side is unequal, the transformation is referred to as a nuclear reaction or radioactive decay.) The type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.Įnergy and entropy considerations are invariably important in almost all chemical studies. The number of atoms on the left and the right in the equation for a chemical transformation is equal. It can be symbolically depicted through a chemical equation, which usually involves atoms as subjects. The basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. Solutions of substances in reagent bottles, including ammonium hydroxide and nitric acid, illuminated in different colorsĪ chemical reaction is a transformation of some substances into one or more different substances. The applications of various fields of chemistry are used frequently for economic purposes in the chemical industry. Over this time frame, it has evolved, and now chemistry encompasses various areas of specialisation, or subdisciplines, that continue to increase in number and interrelate to create further interdisciplinary fields of study. For example, chemistry explains aspects of plant growth ( botany), the formation of igneous rocks ( geology), how atmospheric ozone is formed and how environmental pollutants are degraded ( ecology), the properties of the soil on the moon ( cosmochemistry), how medications work ( pharmacology), and how to collect DNA evidence at a crime scene ( forensics).Ĭhemistry is a study that has existed since ancient times. It is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. In the scope of its subject, chemistry occupies an intermediate position between physics and biology. Chemistry also addresses the nature of chemical bonds in chemical compounds. It is a physical science under natural sciences that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances. Chemistry is the scientific study of the properties and behavior of matter. ![]()
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