Atomic Structure Flashcards
The first ionisation energy
The energy needed to remove one mole of electrons to remove one mole of atoms in their gaseous state to form one mole of 1+ ions which are also in their gaseous state.
Ionisation energy
Ionisation energy is the minimum amount of energy required to remove 1 mole of electrons from 1 mole of atoms in the gaseous state
Factors affecting ionisation energy
Sheilding
Nuclear charge
Atomic size
Sheiilding
The more electrons shells between the positive nucleus and negative electron that is being removed the less energy is required.
There is a weaker attraction.
Ionisation requires energy so they are always an endothermic processes and have a positive value
Nuclear charge
The more protons in the nucleus the bigger the attraction between nucleus and outer electrons.
This means more energy required to remove the electron.
Atomic size
The bigger the atom the further away the outer electrons are from the nucleus.
The attractive force between nucleus and outer electrons reduces – easier to remove electrons.
Successive ionisation
The removal of more than 1 electron from the same atom
Ionisation trends groups
Ionisation energy decreases as we go down a group
The atomic radius increases as we go down the group.
Outer electrons further from the nucleus. Attractive force is weaker.
Energy required to remove an electron decreases.
Shielding increases as we go down the group. More shells between nucleus and outer shell.
Attractive force is weaker.
Energy required to remove an electron decreases.
Ionisation trends periods
Ionisation energy increases as we go across a period
As we go across the period there is an increasing number of protons in the nucleus. This increases the nuclear attraction.
Shielding is similar and distance from nucleus marginally decreases.
More energy required to remove an outer electron. Ionisation energy increases.
Relative Atomic Mass (Ar)
The average mass of an atom of an element when measured on scale on which the mass of an atom of 12C is exactly 12.
Relative Molecular Mass (Mr)
The average mass of a molecule when measured on scale on which the mass of an atom of 12C is exactly 12.
Relative Isotopic Mass
The mass of an atom of an isotope of an element measured on scale on which the mass of an atom of 12C is exactly 12.
In a mass spectrometer, the relative abundance of each isotope is proportional to
the current generated by that isotope at the detector.
Explain how this current is generated.
Electron(s) transferred / flow (at the detector)
(From detector / plate) to the (+) ion
Outline how the TOF mass spectrometer is able to separate these two species to
give two peaks.
Positive ions are accelerated by an electric field
To a constant kinetic energy
The positive ions with m / z of 104 have the same kinetic energy as those with
m / z of 118 and move faster
Therefore, ions with m / z of 104 arrive at the detector first
Explain why the second ionisation energy of boron is higher than the first ionisation
energy of boron.
Electron being removed from a positive ion (therefore needs more energy)
