unit 1.2 basic idea about atoms

• what orbitals are there 


  s, p, d and f
• how many electrons can each orbital hold


  s=2

  p=6

  d=10

  f=14
• how many types of orbitals are there


  s=1

  p=3

  d=5

  f=7
• electron configuration


  1s2 2s2 2p6.....
• factors affecting ionisation energy 


  • atomic radius- force of attraction between the nucleus and outer electrons.
  • shielding- electrons in inner shells repel outer shell electrons
  • size of nucleus- greater nuclear charge, greater attractive force on outer electron
• succesive ionisation energy always increases:


  • same number of protons hold onto fewer + fewer electrons
  • less electron electron replusion makes each shell closer to nucleus
  • distance from electron to nucleus decreases
• atomic spectrum


  frequencies of electromagnetic radiation emitted or absorbed during transitions of elections between energy levels within atoma
• why is nitrogens ionisation energy higher than oxygen

  • 3 half filled orbitals is more stable than one filled and 2 half filled
  • electron electron repulsion between the 2 paired electrons make it easier to remove
• absorption spectrum

  white light is passed through the vapour of an element, certain wavelengths will be absorbed by the atoms and removed from the light as they make the electron gain energy and jump to an excited state. the difference in energy corresponds to frequency and wave length
• ionisation energy


  hxf
• frequency

  $\frac{c}{\lambda}$
• emission spectrum

  atom is given energy electrons are excited. when this source of energy is removed, they fall from a high energy level to a lower energy level and the energy lost is released as a photon of light
• hydrogen spectrum

  only has one electron so has the simplest emission spectra. the balmer series is the only one in the visible light spectrum. when an atom is excited by absorbing energy it jumps up to the excited state and falls back down and emits energy. electrons returning to the n=2 series is when they can be seen on the emission spectra
• why does an atom become unstable

  is it has an unbalance of protons and neutrons in the nucleus
• 3 types of radiation

  • alpha $\alpha$
  • beta $\beta$
  • gamma $\gamma$
• alpha decay

  • split into 2 particles that consist of 2 protons and 2 neutrons (helium nuclei)
  • new nucleus formed will have mass number decreased by 4 and atomic number decreased by 2
• $\alpha$ radiation


  • least penetrating (stop with paper)
  • most ionising (most dangerous)
• beta decay

  • occurs when balance is trying to be restored in the nuclei of an atom
  • particles given out consists of streams of high energy electrons
  • new nucleus will have its mass number unchanged and atomic number increased by 1
• beta radiation

  • can be stopped with aluminium
• gamma decay

  • high energy electromagnetic waves
  • when gamma radiation is emitted there is no effect
• gamma radiation

  • most penetrating, least ionising
  • stopped by lead, has to be thick
• Beta plus- positron emission

  • inverse of beta decay
  • proton is converted into a neutron while releasing a positron and electron neutrino
• beta minus

  • one of the orbital electrons is captured by a proton leading to the formation of a neutron and emission of a neutrino
• half life

  • time taken for half of unstable atoms to decay
  • time taken for activity to halve from its original value
• consequences for living cells

  • damages the DNA of cells, chnages the way cell functions, cause mutations and formation of cancerous cells
• medicine

  • colbalt-60 used as treatment for cancer, gamma radiation
  • technetium-99 most commonly used medical radioisotope used as a tracer
• radio dating

  • carbon-14 half life of 5570 years, used to estimate geological rock age
• magnetic field alpha particles

  • alpha particles are deflected, they are positivly charged
• magnetic field beta particles

  • deflected in the opposite direction of alpha, so they are negatively charged
• magnetic field of gamma rays

  • they pass straight through so have no charge