Contents:
1.1 Atomic Structure
1.2 Amount of Substance
1.3 Bonding and Structure
1.4 Energetics
1.5 Kinetics
1.6 Equilibria
1.7 Oxidation, Reduction and Redox
, Atomic Structure
History of the Atom:
400 BC – Democritus developed the atomic theory; all things are made of indivisible particles which
cannot be destroyed.
1904 – J.J Thomson proposed the Plum Pudding Model: a ball of positive charge that had electrons
scattered within it.
1911 – Rutherford carried out the alpha particle experiment, resulting in the development of the
nuclear model. Experiment showed the atom is mostly empty space with most the mass and all the
positive charge concentrated in the centre, and that electrons moved around the nucleus.
1913 – Bohr discovered electron orbitals and developed his own version of the nuclear model.
Particle Proton Neutron Electron Total electrons in shell = 2n2
Relative Charge +1 0 -1
Relative Mass 1 1 1/1840 Where n = number of the atomic shell
Definitions:
Mass Number – sum of protons and neutrons in an atom.
Atomic Number – equal to number of protons in an atom.
1
Ar – average mass of one atom compared to 12 of the mass of 12C.
Isotope – atoms of the same element with a different number of neutrons.
Ion – atoms that have an overall charge resulting from the loss/gain of electrons.
Mass Spectrometry – technique used to identify different isotopes and find the Ar of an element.
Time of Flight Mass Spectrometry:
Spectra produced shows each isotope present by recording time taken for ions of each isotope to
reach a detector.
• Ionisation:
o Electrospray – sample is dissolved in a volatile solvent and injected through a fine
hypodermic needle to give an aerosol. Tip of needle is attached to positive terminal of
high voltage, where particles are ionised by gaining a proton from the solvent as they
leave the needle. X(g) + H+ → XH+(g)
o Electron impact – sample is vapourised and then high energy electrons are fired at it,
knocking off an electron from each particle and forming a 1+ ion.
• Acceleration: positive ions are accelerated towards a negatively charged detection plate.
• Ion Drift: ions are deflected by a magnetic field into a curved path, where the radius of the
path depends on the charge and mass of the ion.
• Detection: when the ions hit the negatively charged detection plate, they gain an electron
and produce current. The greater the abundance, the greater the current.
Spectra produced by mass spectrometry of chlorine display a characteristic pattern in a 3:1 ratio for
Cl+ ions and a 3:6:9 ratio for Cl2+ ions, because one isotope is more common than the other and the
chlorine molecule can form in different combinations.
1.1 Atomic Structure
1.2 Amount of Substance
1.3 Bonding and Structure
1.4 Energetics
1.5 Kinetics
1.6 Equilibria
1.7 Oxidation, Reduction and Redox
, Atomic Structure
History of the Atom:
400 BC – Democritus developed the atomic theory; all things are made of indivisible particles which
cannot be destroyed.
1904 – J.J Thomson proposed the Plum Pudding Model: a ball of positive charge that had electrons
scattered within it.
1911 – Rutherford carried out the alpha particle experiment, resulting in the development of the
nuclear model. Experiment showed the atom is mostly empty space with most the mass and all the
positive charge concentrated in the centre, and that electrons moved around the nucleus.
1913 – Bohr discovered electron orbitals and developed his own version of the nuclear model.
Particle Proton Neutron Electron Total electrons in shell = 2n2
Relative Charge +1 0 -1
Relative Mass 1 1 1/1840 Where n = number of the atomic shell
Definitions:
Mass Number – sum of protons and neutrons in an atom.
Atomic Number – equal to number of protons in an atom.
1
Ar – average mass of one atom compared to 12 of the mass of 12C.
Isotope – atoms of the same element with a different number of neutrons.
Ion – atoms that have an overall charge resulting from the loss/gain of electrons.
Mass Spectrometry – technique used to identify different isotopes and find the Ar of an element.
Time of Flight Mass Spectrometry:
Spectra produced shows each isotope present by recording time taken for ions of each isotope to
reach a detector.
• Ionisation:
o Electrospray – sample is dissolved in a volatile solvent and injected through a fine
hypodermic needle to give an aerosol. Tip of needle is attached to positive terminal of
high voltage, where particles are ionised by gaining a proton from the solvent as they
leave the needle. X(g) + H+ → XH+(g)
o Electron impact – sample is vapourised and then high energy electrons are fired at it,
knocking off an electron from each particle and forming a 1+ ion.
• Acceleration: positive ions are accelerated towards a negatively charged detection plate.
• Ion Drift: ions are deflected by a magnetic field into a curved path, where the radius of the
path depends on the charge and mass of the ion.
• Detection: when the ions hit the negatively charged detection plate, they gain an electron
and produce current. The greater the abundance, the greater the current.
Spectra produced by mass spectrometry of chlorine display a characteristic pattern in a 3:1 ratio for
Cl+ ions and a 3:6:9 ratio for Cl2+ ions, because one isotope is more common than the other and the
chlorine molecule can form in different combinations.
