| 释义 |
trace element
trace elementn.1. A chemical element present in tiny amounts: trace elements in ground water.2. A chemical element required in minute quantities by an organism to maintain proper physical functioning.trace element n (Biology) any of various chemical elements, such as iron, manganese, zinc, copper, and iodine, that occur in very small amounts in organisms and are essential for many physiological and biochemical processes trace′ el`ement
n. 1. any chemical element that is required in minute quantities for physiological functioning. 2. a substance that occurs naturally only in minute amounts in the earth's crust. Also called trace′ min`eral.[1935–40]trace element (trās) An element present in an organism in only very small amounts but essential for normal metabolism. Iodine and cobalt, for example, are trace elements required by humans.Thesaurus| Noun | 1. |  trace element - an element that occurs at very small quantities in the body but is nonetheless important for many biological processeschemical element, element - any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter |
Translationsoligoélémentmicroelementotrace element
trace element any of various chemical elements, such as iron, manganese, zinc, copper, and iodine, that occur in very small amounts in organisms and are essential for many physiological and biochemical processes trace element[′trās ‚el·ə·mənt] (analytical chemistry) An element in a sample that has an average concentration of less than 100 parts per million atoms or less than 100 micrograms per gram. (biochemistry) A chemical element that is needed in minute quantities for the proper growth, development, and physiology of the organism. Also known as micronutrient. (geochemistry) An element found in small quantities (usually less than 1.0%) in a mineral. Also known as accessory element; guest element. trace element
element [el´ĕ-ment] 1. any of the primary parts or constituents of a thing.2. in chemistry, a simple substance that cannot be decomposed by ordinary chemical means; elements are the basic components of which all matter is composed.
Chemical elements are made up of atoms, each of which consists of a nucleus with a cloud of negatively charged electrons revolving around it. The two major components of the nucleus are protons and neutrons. The number of protons in the atoms of a particular element is always the same, and therefore the physical and chemical properties of the element are always the same. It is possible, however, for a chemical element to exist in several different forms, the difference depending on the number of neutrons in the nucleus of its atoms. Different forms of the same element are called isotopes.
There are at least 105 different chemical elements known. (See Appendix 6 for a list of the elements, and the symbol, atomic weight, and atomic number of each.) The number" >atomic number of an element is determined by the number of protons in the nucleus of one of its atoms. The mass number of an isotope is determined by the total number of neutrons and protons in the nucleus.Stable Chemical Elements. A stable chemical element is one that contains an optimal ratio or range of ratios between the number of protons and neutrons in the nucleus. A stable element does not spontaneously transmute into another element and therefore does not give off radiation. The stable elements are those that have an atomic number below 84, except for a few, such as potassium and rubidium, which are weakly radioactive.Radioactive Chemical Elements. A radioactive chemical element does not contain an optimal proton-to-neutron ratio in its atomic nuclei and therefore readily gives off nuclear particles until all nuclei have attained the optimal combination of protons and neutrons. The spontaneous releasing of its nuclear particles changes the radioactive atom into a new atom (transmutation).
As radioactive elements disintegrate and form new chemical elements, a tremendous amount of energy is released. This emission of energy and nuclear particles is called radiation. The radiations may be electrically charged particles having size and mass, such as alpha particles and beta particles, or they may be nonparticulate and contain no electrical charges, such as gamma rays. Most radioactive elements give off either alpha or beta particles and at the same time emit gamma radiation.formed e's of the blood the blood cells.trace element a chemical element present or needed in extremely small amounts by plants and animals; such elements include manganese, copper, cobalt, zinc, and iron.trace elementn.1. A chemical element present in tiny amounts: trace elements in ground water.2. A chemical element required in minute quantities by an organism to maintain proper physical functioning.trace element Any of a group of metal ions present in minimal amounts in the environment, including arsenic, chromium, cobalt, copper, fluorine, iodine, manganese, nickel, selenium, silicon, tin, vanadium and zinc.trace element any element that is necessary for the proper working of biological systems in concentrations less than 10–5M. Absence can cause disease and death. For example, boron deficiency causes ‘heart rot’ in sugar beet, and cobalt deficiency causes ‘coast disease’ in Australian sheep and cattle. See THYROID GLAND for iodine deficiency, and ESSENTIAL ELEMENTS.LegalSeeElementtrace element
Words related to trace elementnoun an element that occurs at very small quantities in the body but is nonetheless important for many biological processesRelated Words |