Atoms- chemistry

Atoms- chemistry

1. DEFINITIONS

   • Ar= Average mass of an atom of an element relative to 1/12th the mass of an atom carbon-12
   • Isotopes= SAME atomic no. but DIFFERENT mass no. SAME chemical properties but DIFFERENT physicial properties
   • Isotopic abundance= HOW MUCH of each element in an isotope

2. RAM- ((75x35) + (25x37))divided by 100

3. THE MOLE

   • Mole= one mole is always the same number of particles
   • 1.) Write equation 2.) Turn into moles 3.) Ratio 4.) Convert back
   • Molar volume= 1 mole of any gas occupies 24dm3 at standard temperature(25C) and pressure(1)

4. MASS SPECTROMETRY

   • Get the isotopic composition
   • Get RAM of element
   • For radioactive dating, space research, sport detecting drugs
   • The electron gun knocks off electrons to make sample +ve

5. IONISATION ENERGIES

   • Evidence of electron shells that orbit the nucleus
   • Energy needed to REMOVE one mole of electrons from one mole of atoms of an element in the GASEOUS state, to form one mole of singly charged POSITIVE ions
   • 1st ionisation energy= M ---> M+ + e-
   • 2nd ionisation energy= M+ ----> M2+ + e-
   • 3rd ionisation energy= M2+ ---> M3+ + e-
   • Ionisation energies increase with the number of electrons removed
   • Energy levels= s=2, p=6, d=10, f=14
   • Less energy needed for the electrons in the outer shell

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