Isotopes, TOF, Electron Arrangement And Ionisation Energies Flashcards
What is an isotope
Atoms with same number of protons but a different number of neutrons. Atomic number is the same but the mass number is different. Same chemical properties (reactions) different physical (boiling points)
What is the relative atomic mass
Ar= the mass of one atom compared with 1/12 of the mass of an atom of carbon-12
Total weight
How to work out relative atomic mass
(%abundance x mass number) / 100
What is the mass spectrometer for
Measuring the mass of a species from single atoms to complex molecules
What is relative molecular mass
Mr= relative molecular mass of an element or compound, is the sum of the Ar of all the atoms in the molecule divided by 1/12 of the mass of an atom of carbon -12
How does time of flight mass spectrometry work
The ions injected through hypodermic needle into the electric files which accelerates ions so they all have the same kinetic energy. They then drift through a hole in the negative plate forming a beam, the lighter ones have higher velocities so are detected first
Why does the tube need to be a vacuum
So that air particles don’t collide with the ions and affect the results
What are the two types of ionisation
Electron impact and electrospray
Explain ionisation through electron impact
High energy electron from electron gun fired at sample knock off an electron
Facts about electron impact
Can create fragments Best used on elements and small molecules Vintage method Could be a filament lamp Sample must already be gas
Explain ionisation through electrospray
Sample dissolved in volatile substance, injected through a hypodermic needle forming an aerosol or fine mist. Tip of the needle has high voltage, each ion gains a proton through the needle, useful for large molecules that could otherwise form complicated fragments
What does the graph tell you
The molecular ion will have the greatest mass so is the peak on the right
What is the first ionisation energy
Energy required to remove one electron from each atom in a mole of gaseous atoms producing one mole of +1 gaseous ions
How does ionisation energy change down the group
Easier to ionise
Atoms get bigger radius is larger
More shielding
Weaker attraction from nucleus to electron in outer shell
What is dative covalency
Bonding occurs when one atom provides both electrons for the covalent bond.
