Atomic Structure

A set of definitions for atomic structure: and maybe more...


Mass numbers and isotopes

Mass number- the number of protons and neutrons in the nucleus of one atom of an element.

Relative atomic mass- the average mass of one atom of an element/one twelfth the mass of one atom of carbon-12.

Atomic number- the number of protons in the nucleus of an atom.

Isotope: atoms of the same element but with different mass numbers. 

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Mass Spectrometry

Ionisation- The gaseous atoms are ionised by knocking one or more electrons off using an electron gun to give a positive ion. 

Acceleration-The positive ions are accelerated by an electric field and focused by passing through a series of slits.

Deflection- The fast moving beam of electrons are deflected by a strong electromagnet. The magnitude of deflection depends on the mass:charge ratio. If m/z is small, the deflection is large.

Detection- The ion hits the detector and accepts an electron from the detector which creates a small current. This current is amplified and produces a signal on a computer.

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First Ionisation Energy

First ionisation energy- The enthalpy change for the removal of one mole of electrons from one mole of atoms of an element in the gas phase.

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