Chemistry cp2

• Positive Rays

  Also called canal rays, produced when electric current is passed through gas at low pressure
• Positive Rays


  • Have positive charge, deflected towards negative pole of electric field
  • Move in straight line
  • Smaller em ratio than electron
  • Depends on gas filled in tube
  • Obtained highest em ratio when H2 gas was filled
  • Have very low penetration power
  • Can ionize gases
  • Produce shadow of an opaque object
  • Less mass = more em ratio
  • Traveled through perforated cathode electrodes
• Particle


  Alpha: Positive charge, He

  Beta: Negative charge

  Neutron: No charge

  Proton: Positive charge, H+
• Electron charge: -1.6022x10^-19 C

  Proton charge: +1.6022x10^-19 C

  Neutron: No charge
• Electron mass: 9.1095x10^-31 kg

  Proton mass: 1.6726x10^-27 kg

  Neutron mass: 1.6750x10^-27 kg
• Relative mass: Electron 1, Proton 1836 times, Neutron 1840 times
• Relative charge: Electron -1, Proton +1, Neutron 0
• Orbital


  Region around the nucleus where electrons are likely to be found
• Electronic configuration


  Distribution of electrons in shells, sub-shells and orbitals of an atom according to definite rules
• Discovery of Positive Rays

  Apparatus: Discharge tube with perforated cathode

  Procedure: High potential difference applied, cathode rays strike gas molecules, positive ions produced

  Observation: Positive rays pass through perforated cathode and produce reddish glow on opposite wall
• Radius of an orbit

  Proportional to n^2, where n is the principal quantum number
• Energy of revolving electron

  Inversely proportional to n^2, where n is the principal quantum number
• Hydrogen spectrum


  • Consists of several sharp spectral lines in visible, ultraviolet and infrared regions

  Can be classified into 5 spectral series: Lyman, Balmer, Paschen, Brackett, Pfund
• Quantum numbers


  Numerical values that give acceptable solutions to Schrodinger wave equation

  Principal quantum number (n)

  Azimuthal quantum number (l)

  Magnetic quantum number (m)

  Spin quantum number (s)
• Aufbau principle: Electrons are filled in energy sub-shells in order of increasing energy values
• Pauli's exclusion principle: Two electrons in the same orbital must have opposite spins
• Hund's rule: When filling degenerate orbitals, electrons are placed in separate orbitals with the same spin rather than in the same orbital with opposite spins
• Hydrogen


  Atomic Number 1
• Helium


  Atomic Number 2
• Lithium


  Atomic Number 3
• Beryllium


  Atomic Number 4
• Boron


  Atomic Number 5
• Carbon


  Atomic Number 6
• Nitrogen


  Atomic Number 7
• Oxygen


  Atomic Number 8
• Fluorine


  Atomic Number 9
• Neon


  Atomic Number 10
• Sodium


  Atomic Number 11
• Magnesium


  Atomic Number 12
• Aluminium


  Atomic Number 13
• Silicon


  Atomic Number 14
• Phosphorus


  Atomic Number 15
• Sulphur


  Atomic Number 16
• Chlorine


  Atomic Number 17
• Argon


  Atomic Number 18
• Potassium


  Atomic Number 19
• Calcium


  Atomic Number 20
• Scandium


  Atomic Number 21
• Titanium


  Atomic Number 22
• Vanadium


  Atomic Number 23