trace element

trace element (trs)

n.

1. A chemical element required in minute quantities by an organism to maintain proper physical functioning.

2. A minute quantity or amount, as of a chemical compound.

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trace element

Etymology: L, trahere, to draw, elementum, first principle

an element essential to nutrition or physiologic processes, found in such minute quantities that analysis yields a presence of only trace amounts.

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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 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).ƒ

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.

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trace element,

n an element essential to nutrition or physiologic processes, found in such minute quantities that analysis yields a presence of virtually none.

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trace element

essential ingredients of the diet of a particular species of animals but the amount required is very small. Includes copper, cobalt, iron, iodine, manganese, molybdenum, selenium and zinc. Chromium, fluorine and silicon are also necessary in some experimental diets but their addition to livestock diets is not considered to be essential. See also macroelement. Called also trace minerals.