Chemistry AS - Atomic and Electronic Structure

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  • Created by: Rebecca
  • Created on: 28-04-10 10:55

Relative Atomic Number - the number of protons in the nucleus compared to the number in carbon-12. To calculate from a mass spectometer graph its the (ratio of one isotope x by its Mr) + (ratio of another isotope x by it's Mr) divided by the sum of the ratios.

Mass number - the number of protons and the number of neutrons compared to the number in carbon-12

Mass spectrometry Steps

Vaporisation - some of the substance is injected into machine. The high vacuum causes it to vapourise is it's not already a gas

Ionisation - the vapourised substance is then bombarded with a beam of high-energy of electrons. This knocks off electrons in the sample forming positive ions.

Acceleration - the now positive ions from the sample are accelerated by a plate with a negative potential because opposite charge repel.

Deflection - A magnetic field deflects the moving ions from the sample. The lighter ions are deflected more than the heavier ones

Detection - the ions are detected as a tiny current and the detector sends a signal to a computer where a graph is produced.

Isotopes - atoms of the same element with the same atomic number but different mass number. This is because they all have the same number of protons but different number of neutrons.

Relative Isotopic Mass - the mass of one atom of an isotope compared to the mass of one atom of carbon-12.

Relative Molecular Mass - the furthest peak on the right on a mass spectrometer graph is the mass of the whole

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