Chemistry - Topic 1

Define Ionisation Energy
the energy required to remove one mole of electrons from one mole of GASEOUS atoms of an element
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What is the trend in successive ionisation energies
They get LARGER as the resulting cations hold on to their electrons with a larger force of attraction
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What are the 4 factors affecting Ionisation energy
(1) Nuclear charge (2) distance from nucleus (3) shielding (4) spin pairing [subtle]
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What is shielding
the number of electrons between the outer electron and the nucleus. the inner electrons decrease the strength of the effective nuclear charge, so the outer electron is held less strongly
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What is the trend in ionisation energy going DOWN a group
it DECREASES as despite the increase in nuclear charge, there are more shells so outer electron is further from the nucleus (stronger shielding effect), and so the outer electron is held less strongly
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What is the trend in ionisation energy going ACROSS a period
it INCREASES: as nuclear charge increases, the attraction between outer shell and nucleus increases. atomic radius decreases. negligible increase in shielding.
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Define Mass Spectrometry
a way to compare the relative atomic masses of atoms or molecules. it separates atoms+molecules according to their mass and shows how many atoms are present
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What are the 5 stages of Mass Spectrometry
(1) Vaporisation (2) Ionisation (3) Acceleration (4) Deflection (5) Detection
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What happens in VAPORISATION stage in mass spectrometry
The species is turned into vapour (gas)
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What happens in IONISATION stage in mass spectrometry
A beam of electrons bombard the sample and turns atoms ---> ions : e- + X --> X+ + e- + e-
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What happens in Acceleration, Deflection + Detection stage in mass spectrometry: METHOD 1 (electric field)
An electric field accelerates ions into a magnetic field, which deflects them. The ions with the greatest mass + smallest charge is deflected the least. Ions hit a detector, producing an electrical current, as more ions hit the same spot, taller peak
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What happens in Acceleration, Deflection + Detection stage in mass spectrometry: METHOD 2 (field free)
Ions are accelerated into a field free region, and the time taken to hit the detector is measured. The kinetic energy is the same for all ions but the speed is affected by the mass. Heavier ions are therefore slower.
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Define Isotope
atoms of the same element with the same proton number but a different neutron number
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Isotopes have the same....
proton number, electron number, atomic number, chemical properties
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Isotopes have different....
neutron number, mass number, physical properties
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Define Relative Atomic Mass
the average mass of an atom of an element relative to 1/12th the mass of an atom of carbon 12 isotope
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Define Relative Molecular Mass
the sum of the RAMs of all the atoms in the molecular formula
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Orbitals
electrons travel in orbitals with discrete quantised speeds+energies, not every one is possible. electrons can only gain + lose energy by jumping from one orbital to another. This change in energy is accompanied by emission or absorption of light.
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How many electrons are in the first 4 shells?
2 8 18 32
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The 3 rules of electron orbitals
(1) electrons go to the lowest energy level first (2) there are 2 electrons per orbital (3) each orbital fills single before spin pairing
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4s and 3d orbital energy levels
As shells get further from the nucleus, they become closer in energy. There is an overlap between 3d+4s, as 4s has a lower energy level than 3d. Electrons fill 4s-->3d-->4p
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Why is the IE of Aluminium lower than Magnesium?
The outer electron in Al is in a p sub shell. This is higher in energy than the outer electron in Mg (s sub shell). The outer electron in Al is shielded by s sub shell so it is easier to remove.
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Why is the IE of Oxygen lower than Nitrogen?
Oxygen=2p^4. Nitrogen=2p^3. The outer electron in oxygen is spin paired. v
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Card 2

Front

What is the trend in successive ionisation energies

Back

They get LARGER as the resulting cations hold on to their electrons with a larger force of attraction

Card 3

Front

What are the 4 factors affecting Ionisation energy

Back

Preview of the front of card 3

Card 4

Front

What is shielding

Back

Preview of the front of card 4

Card 5

Front

What is the trend in ionisation energy going DOWN a group

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Preview of the front of card 5
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