أكتوبر 22nd, 2018

 

Atomic spectrometry

Atomic spectrometry A branch of chemical analysis that seeks to deter­mine the composition of a sample in terms of which chemical elements are present and their quantities or concentrations. Unlike other methods of elemental analysis, however, the sample is decomposed into its constituent atoms which are then probed spectroscopically.

In routine atomic spectrometry, a device called the atom source or atom cell is responsible for producing atoms from…

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Atomic number

Atomic number The number of elementary positive charges (protons) con­tained within the nucleus of an atom. It is denoted by the letter Z. Correspondingly, it is also the number of planetary electrons in the neutral atom.

The concept of atomic number emerged from the work of G. Moseley, done in 1913-1914. He measured the wavelengths of the most energetic rays (Kand L lines) produced by using the elements…

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Atomic nucleus

Atomic nucleus The central region of an atom. Atoms are composed of nega­tively charged electrons, positively charged protons, and electrically neutral neutrons. The protons and neutrons (collectively known as nucleons) are located in a small central region known as the nucleus. The electrons move in orbits which are large in comparison with the dimensions of the nucleus itself. Protons and neutrons possess ap­proximately equal masses, each roughly 1840…

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Atomic mass unit

Atomic mass unit An arbitrarily defined unit in terms of which the masses of individual atoms are expressed. One atomic mass unit is defined as exactly 1fi2 of the mass of an atom of the nuclide 12C, the predominant isotope of carbon. The unit, also known as the dalton, is often abbreviated amu, and is designated by the symbol u. The relative atomic mass of a…

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Atomic mass

Atomic mass : The mass of an atom or molecule on a scale where the mass of a carbon-12 (12C) atom is exactly 12.0. The mass of any atom is approximately equal to the total number of its protons and neutrons multiplied by the atomic mass unit, u = 1.6605397 x 10-24 gram. (Electrons are much lighter, about 0.0005486 u.) No atom differs from this simple formula by…

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