Atomic Structure

Atomic Structure

Fundamental Particles that compose atoms
1. Protons
  1. Found in nucleus
  2. relative mass = 1
  3. Relative charge = +1
2. Neutrons
  1. Found in nucleus
  2. Relative mass =1
  3. Relative charge = 0
3. Electrons
  1. Surround the nucleus
  2. Relative mass = 1/1840
  3. Relative Charge = -1
The arrangement of the electrons
1. Electron shells
  1. 1st shell = 2 electrons
  2. 2nd shell = 8 electrons
  3. 3rd shell = 18 electrons
2. General formula
  1. number of electrons in shell = 2n²
3. Electron Diagrams
  1. write the number of electrons in each shell,
    1. inner shell first
  2. Separate numbers with a comma
  3. e.g carbon would be 2,4
Mass number, atomic number and isotopes
1. Mass Number, A
  1. Number of protons + number of neutrons
  2. the is because the electrons weigh virtually nothing
2. Atomic Number, Z
  1. Equal to the number of protons
  2. All atoms of the same element have the same atomic number.
3. Isotopes
  1. Atoms with the same number atomic number, but a different mass number
  2. i.e they have a different number of neutrons
Mass Spectrometry
1. Ionisation
  1. beam of electrons knock an electron form the outer shell of the sample
  2. This makes them positive ions
2. Acceleration
  1. Positive ions are attracted to negatively charge plates
  2. Causing the ions to accelerate, the lighter they are the faster they go
  3. Deflection
    1. beam is moved into a magnetic field at right angle to the direction of travel
    2. Deflection depends on the ratio of its mass to charge, heavier ions are deflected less
3. Detection
  1. The magnetic field is gradually increased so that the ions enter the detector one after another
  2. The ions strike the detector and accept an electron so they are no longer ions

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