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Flashcards

1. Atomic structure and the periodic table

Georgina Peck A Level Chemistry A level English 25 cards

Structure of an atom

Cards in this deck (25)

  1. 1Structure of an atomEnter text here...Structure of an atom
  2. 2Mass numberthe number of protons and neutrons in the nucleus
  3. 3Atomic numberthe number of protons in the nucleus
  4. 4Isotopesatoms that have the same number of protons and electrons but different numbers of neutrons
  5. 5Relative atomic massthe weighted mean mass of an atom of an element compared to 1/12 the mass of an atom of carbon-12, which has a mass of 12
  6. 6Relative isotopic massthe mass of an atom of an isotope of an element compared to 1/12 the mass of an atom of carbon-12, which has a mass of 12
  7. 7The mass spectrometer1. The sample is injected into the mass spectrometer and is vaporised
    2. The vapour is bombarded with high-energy electrons, which collide with atoms of the sample. Electrons are removed from the atoms in the sample forming positive ions
    3. The positive ions are accelerated by an electric field
    4. A vacuum pump ensures that no air molecules are present in the mass spectrometer
    5. The positive ions are deflected by a magnetic field. The amount by which they are deflected depends on both the mass of the ion(m) and the charge(z) on the ion. Ions with a larger m/z ratio are deflected less than ions with a smaller m/z ratio
    6. The positive ions are detected. The number of ions passing through the machine at each magnetic field setting is measured. It shows the number of ions at each different m/z ratio present in the sample    The mass spectrometer
  8. 8Molecular ion peakthe peak with the highest m/z ratio in the mass spectrum, the M peak
  9. 9Quantum shella quantum shell defines the energy level of an electron
  10. 10Orbitala region within an atom that can hold up to two electrons with opposite spins
  11. 11S - orbitalEnter text here...S - orbital
  12. 12P - orbitalEnter text here...P - orbital
  13. 13D - orbitalD - orbital
  14. 14Electronic configurationEnter text here...Electronic configuration
  15. 15Hund’s ruleelectrons will occupy the orbitals singly before pairing takes place
  16. 16Pauli exclusion principletwo electrons cannot occupy the same orbital unless they have opposite spins
  17. 17First ionisation energythe energy required to remove an electron from each atom in one mole of atoms in the gaseous stateFirst ionisation energy
  18. 18Second ionisation energythe energy required to remove an electron from each singly charged positive ion in one mole of positive ions in the gaseous stateSecond ionisation energy
  19. 19Factors that affect the energy an electron has• The orbital in which the electron is in
    • The nuclear charge of an atom
    • The repulsion experienced by the electron from all the other electrons present
  20. 20Trends in ionisation energies - across a period• The nuclear charge increases as the number of protons increase. This leads to an increase in attraction between the nucleus and the electron, and therefore a decrease in the energy of the outermost electron, and an increase in first ionisation energy
    • One more electron is added to the same quantum shell and this increases the electron – electron repulsion within the quantum shell. This causes an increase in energy of the outermost electron, and would lead to a decrease in first ionisation energy
    • The increase in nuclear charge overcomes the increase in electron-electron repulsion, so there is a general increase in first ionisation energy
  21. 21Trends in ionisation energies - down a group:• The nuclear charge increases as the number of protons increases. This leads to an increase in attraction between the nucleus and the electron, and therefore a decrease in the energy of the outermost electron, and an increase in first ionisation energy
    • One new quantum shell is added on each occasion. This increases the energy of the outermost electron as each quantum shell has a higher energy value than the previous and as each new quantum shell is added, the outer electron experiences increased repulsion from the inner electrons
    • The effect of adding an extra shell and increasing the shielding is more significant than the increase in nuclear charge, so the first ionisation energy decreases
  22. 22Successive ionisation energies• As each successive electron is removed from a quantum shell, the electron-electron repulsion within the shell decreases. This results in a decrease in the energies of the remaining electrons, and therefore an increase in ionisation energy
    • Large increase in ionisation energy from one shell to the next
  23. 23The periodic tableGroups: the vertical columns in the periodic table
    Periods: the horizontal rows in the periodic table
    The periodic table is also divided into blocks    The periodic table
  24. 24Periodicitya regularly repeating pattern of atomic, physical and chemical properties with increasing atomic number
  25. 25Atomic radiiThe atomic radius of an element is the distance from the centre of the nucleus to the boundary of the electron cloud. Atomic radius:
    • Decreases across a period
    • Increases from one period to the next
    There is a negligible increase in shielding going across a period, but the nuclear charge increases. This increases the force of attraction between the nucleus and outer electrons

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A level A Level Chemistry Flashcards on 1. Atomic structure and the periodic table, created by Georgina Peck on 13/01/2017.
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