Atomic structure

• First ionization energy (IE) is the energy required to remove a mole of electrons from a mole of atoms in the gaseous state to give a mole of gaseous ions, each with one positive charge
• Trend in ionization energy across a period: As nuclear charge increases, electrons become harder to remove, leading to an increase in ionization energy across a period
• Trend in ionization energies down a group: As the outer electrons get further from the nucleus, less energy is needed to remove them
• The 4s sub-shell has a lower energy than the 3d sub-shell, so it is filled first
• How sub-shells are filled

  1. Fill from the bottom

  2. Each orbital can have only two opposite electrons

  3. Electrons repel, so fill orbitals singly before pairing
• Second electron shell

  • One s-sub-shell with one s-orbital, and a p-sub-shell with three p-orbitals
• Third electron shell

  • One s-orbital, three p-orbitals, and five d-orbitals
• A big jump in ionization energy can be seen between shells
• Generally, there is a decrease in ionization energy down a group
• Electronic structure

  Electrons can be thought of as a cloud of negative charge. An orbital is a way of defining the energy of an electron. Each orbital can hold two electrons of opposite spin
• How sub-shells are filled

  1. Fill from the bottom

  2. Each orbital can have only two, opposite electrons

  3. Electrons repel, so fill orbitals singly before pairing

  4. The 4s sub-shell has a lower energy than the 3d, so is filled first
• Protons and neutrons have approximately the same mass, so to make things easier we say they each have a mass of 1 atomic mass unit (amu). Electrons have a mass of approximately 9.11×10^-31 kg
• Isotopes are atoms of an element that have the same number of protons but different numbers of neutrons
• All relative atomic masses are based on the mass of 12C, which has a mass of exactly 12 atomic mass units
• The mass number (A) is the total number of protons and neutrons in an atom: A = no. of protons + no. of neutrons
• The electron arrangement in phosphorus can be written as 2,8,5 or 1s²2s²2p⁶3s²3p³
• Electron shells and sub-shells

  • Each s-orbital is spherical, whilst the p-orbitals are a dumbbell shape
• First ionisation energy (IE) is the energy required to remove a mole of electrons from a mole of atoms in the gaseous state to give a mole positive charge
• The charge of a proton is +1.602x10^-19 C, while the charge of an electron is -1.602x10^-19 C
• The atomic number Z is the number of protons (and also the number of electrons) in an atom
• Protons and neutrons have the same mass, 1.673x10^-27 kg, while electrons have a mass of (almost) 0, which is 9.11×10^-31 kg
• Structure of an atom

  • The atomic number Z is the number of protons (and also the number of electrons) in an atom
  • The mass number A is the total number of protons and neutrons in an atom: A = no. of protons + no. of neutrons
  • Isotopes are atoms of an element that have the same number of protons but different numbers of neutrons
• Properties of subatomic particles

  • Relative mass
  • Relative charge
  • Location
• Protons and electrons have opposite charges: the charge of a proton is +1.602×10^-19 C, and an electron has a charge of -1.602x10^-19 C
• Electrons can act as waves or particles
• Rutherford's gold foil experiment and the idea of the nucleus developed

  1911
• The relative atomic mass (Ar) is the average mass of an atom of an element relative to one twelfth of the mass of an atom of carbon-12
• Relative atomic mass (Ar) formula

  (Mass of 1st isotope × abundance 1)+ (Mass of 2nd isotope × abundance 2) + (Mass of 3rd isotope × abundance 3) ÷100
• Chemical properties are determined by the number of electrons
• Calculating mass of a single atom formula

  Mass (g) = relative mass (g/mol) ÷ Avogadro's constant (L) which 6.022 × 10²³ mol -1
• Avogadro’s constant is used to calculate how many atoms there are in one mole of any substance.
• Time of Flight Mass Spectrometer stages

  1. First the element has to be ionised this is done by two ways. One of those ways is electrospray where the sample of different elements is dissolved in a solvent. It's then pass through a fine needle with a high positive voltage. This causes an electron or more to be kicked off turning the element to an ion. The second way is electron bombardment where electrons are fired at the sample causing electrons in the sample to be knocked off and removed.
• The Time of Flight Mass Spectrometer part 2

  1. The next stage is acceleration where the now positive ions would be attracted to a negatively charged plate causing them to accelerate to it . The faster ions would be the ones with a bigger charge and a smaller mass. This is all done in an electric field
• Time of Flight mass spectrometer

  The sample of ions is put into a spectrometer which is a vacuum to remove any air particles that would bump into the ions and slow then down
• Time of Flight Mass Spectrometer part 3

  The ions go through ion drift which is the flight path for the ions going towards the detector
• Time of Flight Mass Spectrometer part 4

  The ions reach the detector most at different times. The detector gives an electron or electrons to the ions this creates a current. This is proportional to their abundance of the ions
• Mass number = protons + neutrons
• Mass spectrometry calculations ( kinetic energy)

  $KE =$$1/2×m×v^2$

  Where KE is kinetic energy measured in joules (J) , m is mass measured in kg and v is velocity measure in m/s