Atomic structure

Cards (27)

  • What does the atomic number tell us about an element?
    The number of protons
  • Define relative atomic mass.
    The average mass of an of an element relative to the 1/2 the mass of an atom of carbon-12
  • Define an isotope.
    Different forms of the same element, which has the same number of protons but different number of neutrons.
    So they have the same chemical properties.
  • Outline process of electrospray ionisation
    • The sample is dissolved in a volatile solvent
    • Then is injected with a fine hypodermic needles to create an aerosol
    • The end of the needle is attached to a high voltage power supply
    • Producing an xH+ ion
  • Outline the process of electron impact ionisation
    • The sample is vaporised
    • Then the electron gun knocks of one electron from the molecule
    • Forming a X+ ion and an electron
  • Define the first ionisation energy
    The amount of energy required to remove one mole of electrons from one mole of gaseplus atoms to form one mole of gaseous 1+ ions

  • Describe how time of flight mass spectrometer works
    1. Ionisation - electrospray or electron impact
    2. Acceleration - the ions are accelerated so they all have the same kinetic
    3. Ion drift - all the ions move at the same kinetic energy (larger mass = slower velocity) (smaller mass = higher velocity)
    4. Detection
  • How are the ions in mass spectroscopy detected and measured?
    Positive ions hit the negatively charged plate and pick up an electron. The movement of electrons causes a current which can then be measured.
  • Time of flight Equation
    t=t=d(2root)m/2KEd(² root)m/2KE
  • How do you calculate Ar
    Ar = (mass × abundance) + (mass × abundance) / total abundance
  • Kinetic energy equation
    Ke=Ke =1/2mv2 1/2 mv²
  • Calculating velocity using Ke
    V = (² root) 2Ke/m
  • What is the molecular ion peak?
    The last significant peak on the graph
  • On a mass spectrum for electronic impact what are many smaller peaks together showing?
    Fragmentation
  • On a mass spectra for electrospray Ionisation, what are smaller peaks due to?
    Isotopes (e.g. C¹³ or H²)
  • Equation for the first Ionisation energy if Al
    Al(g) -> Al+(g) + e‐
  • Equation for the second ionisation of Ca
    Ca+(g) -> Ca2+(g) + e‐
  • Equation for the third Ionisation energy of Fe
    Fe2+(g) -> Fe3+(g) + e-
  • From a series of Ionisation energies of an element, how would you find which group its in?
    Look for the large jump in Ionisation energies ( e.g 4 -> 5th means its in group 4)
  • Name the 3 factors effecting Ionisation energies:
    • Distance from nucleus
    • Nuclear charge
    • Shielding
  • How does shielding effect the Ionisation energy?
    Attraction from the nucleus is shield by inner electrons
    More shells = more shielding = less energy needed to remove electrons
  • How does nuclear charge effect Ionisation energies?
    • Greater nuclear charge = more protons (increased attraction between nucleus and outer e-)
    • So more attraction = more energy needed to remove
    • As e- are removed number of protons remains the same = greater nuclear charge
  • How does distance from nucleus effect Ionisation energy?
    • Further away the outer e- from nucleus = less attraction between them
    • So less energy need to remove them
  • Why is there a did in the transect of first ionisation energies of period 3 elements at aluminium?
    • The outer e- is in the 3p sub-shell, which is slightly further away from nucleus and has shielding from 3s, so takes slightly less energy to remove
  • Why is there a did in the transect of first ionisation energies of period 3 elements at sulfur?
    • Two electrons are paired in the 3p orbital
    • So there's e- e- repulsion means it requires slightly less energy to remove it
  • Why does the first ionisation energy decrease down the group?
    • Atoms get bigger, so electrons removed from higher energy level
    • The other e- is further from the nucleus
    • More shielding
    • Less attraction between e- and nucleus
    • Less energy need to remove the e-
  • Why is there a big jump in ionisation energies?
    After all electrons have been removed from on sub-shell it moves to the next
    • Less shielded = stronger attration = more energy needed