How it works (5 basic steps): detection: positive ions of a particular mass/charge ratio are detected and a signal is sent to a recorder. Ions with higher charges are deflected more as they interact more effectively with the magnetic field. Ions with smallermasses are deflected morethan heavier ions. The magnetic field causes the ions to be deflected, and the amount of deflections is proportional to thecharge/mass ratio. deflection:ions are then passed over an external magnetic field. How it works (5 basic steps): acceleration:resulting unipositive ions pass through slits in parallel plates under the influence of an electric field. In practice, the instrument is set so that only ions with a single positive charge are formed (M+). How it works (5 basic steps): ionization: sample is bombarded with a stream of high energy electons. How it works (5 basic steps): vaporization:if the sample is not already as gas, the sample is heated to this point. The Mass Spectrometer Relative atomic masses (among other things we will discuss when we get to organic chemistry) can be determined using this instrument. Determine the relative atomic mass of chlorine. Thus, naturally occurring chlorine contains 75% and 25%. Example: The two isotopes of chlorine occur in the ratio of 3:1. RELATIVE ATOMIC MASS:weighted mean molar mass of atoms of elements. ISOTOPES Isotopes: atoms that have the same # of protons, but a different # of neutrons. Example:Isotopes of carbon 6p+, 6e-, 6n 6p+, 6e-, 8n Shorthand notation for an atom or ion MASS #: # protons + # neutrons n+/n- A X Z CHARGE: leave blank if n=0 (neutral atom) ATOMIC #: # protons (which is = # electrons if a neutral atom)Įxamples 4 9 4 5 4 20 40 20 20 18 17 37 17 20 18 Periodic Key 6 C Carbon 12.011 Atomic number (Z) Element’s symbol Element’s name Atomic mass (A) # of protons = Z # of electrons = # of protons (in a neutral atom) # of neutrons = A-Z Actual charge of an electron: 1.602 x 10-19 Coulombs.Actual mass of a proton: 1.672 x 1024g.Relative mass and charge of subatomic particles Ernest Rutherford Ernest Rutherford (1871 - 1937) 1908 Nobel Observations: 1) Most of the particles passed directly through - no deflection2) Some of the particles were deflected somewhat from their path.3) Some of the particles bounced back in the same direction from which they approached the gold foil. ![]()
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