(2): atoms and reactions

• atomic number is number of protons which is the same as the number of electrons
• relative atomic mass is number of protons + neutrons
• isotopes have different amounts of neutrons
• relative isotopic mass is the mass of an atom of an isotope compared with one twelfth of an atom of carbon-12. equation: mass of an isotope/mass of 1/12 of carbon-12
• relative atomic mass is the weighted mean mass of an atom of an element compared with 1/12th the mass of carbon-12
• the relative mass of a proton is 1, of a neutron 1 and of an electron 1/2000
• most of the mass of an atom is concentrated in the nucleus but the diameter of the nucleus is tiny compared to the whole atom. Orbitals where electrons whizz around the nucleus, take up most of the volume of an atom
• the number and arrangement of electrons decide the chemical properties of an element so isotopes have the same chemical properties because they have the same electronic configuration, just different number of neutrons
• isotopes have different physical properties, e.g density, as physical properties tend to depend more on the mass of the atom
• mass spectrometry can be used to help identify an unknown compound, find the relative abundance of each isotope of an element and determine structural information about a molecule
• equation with number of moles and particles?

  number of moles= number of particles you have/number of particles in a mole
• what is meant by ionic bonding?


  electrostatic forces of attraction between positive and negatively charged ions
• what is meant by 'covalent bond'?

  shared pair of electrons
• mass spectra helps you find the Ar by..

  • multiplying each m/z value by its abundance
  • adding these together and then dividing by the Total abundance (adding the abundance's together- should add to 100)
  • so Ar = sum of (m/z x abundance)/total abundance