Chemistry - Atomic Structure (1.1)

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Plum Pudding Model
Positive 'pudding' with negative electrons.
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Rutherford
Positive alpha particles at sheet of gold. Most passed through, some deflected backwards. Concluded tiny, positive nucleus, electron 'cloud' and mostly empty space.
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Bohr's Model
Realised would spiral and collapse, so must be shells, orbitals, fixed energy and elecromagnetic radiation.
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Quantum Model.
Includes sub-shells.
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Relative Atomic Mass
Average mass of an atom of an element on a scale where carbon-12 is exactly 12g. Isotopic masses x Percentages / Total Percentage (100)
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Mass Spectrometer
Machine used to analyse elements/compounds. 1. Atoms ionised (electrospray ionisation/electron impact). 2. Acceleration. 3. Ion Drift. 4. Detection.
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Electrospray Ionisation
High voltage applied to sample in polar solvent cause it to gain a proton, forming MH+.
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Electron Impact
Sample bombarded by high energy electrons, causing sample to lose an electron due to repulsion , forming M+.
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Acceleration
Positive ions accelerated by electric field. Lower m/z (mass/charge) = lighter and faster.
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Ion Drift
Ions leave electric field with constant speed and kinetic energy. Timed.
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Detection
Detector detects current created when ions hit it. M+ + e - -> M. Lower m/z reach in less time.
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Why is it necessary to ionise molecules for a TOF mass spectrometer?
- They need to cause a current to be detected.- Ions will interact with and be accelerated by an electric field (unlike molecules)
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Why does the mass spectrum of tellurium have a small peak at m/z 64?
Because a 2+ ion was formed (2 electrons removed or 2 protons gained) from 128Te.
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What do chemical properties rely on?
Arrangement of electrons. (Isotopes have same chemical properties)
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What do physical properties rely on?
Mass of the atom (isotopes have different physical properties eg. density)
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s sub-shell
2 electrons (1 orbital)
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p sub-shell
6 electrons (3 orbitals)
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d sub-shell
10 electrons (5 orbitals)
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f sub-shell
14 electrons (7 orbitals)
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Why do electrons fill the sub-shells in a non-linear way eg. 4s before 3d?
Because electrons fill the lowest energy sub-shell first.
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What are the exceptions?
Chromium and Copper - fill 3d before 4s
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Orbitals
Hold 2 electrons of opposite spin. Electrons fill singly before sharing due to repulsion.
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First Ionisation Energy
Energy required to remove first electron from an atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions. M(g) ---> M+(g) + e-
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Factors affecting FIE
Nuclear Charge, Distance from nucleus and Shielding.
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Second Ionisation Energy
Energy required to remove an electron from each ion in 1 mole of gaseous 1+ions. M(g)+ --> M(g) 2+ + e-. Greater than FIE because positive ion.
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FIE trend going down group 2
Decreases - extra shell shield and increases distance.
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FIE trend going across a period
Increases - no. protons increases (stronger nuclear attraction) with same shielding and distance.
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Exceptions of FIE trend in period 3
Aluminium - outer electron in 3p (more shielding and distance). Sulphur - outer electrons in 3p orbital begin to pair and repel.
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Trend of successive ionisation energies within each shell
Increase - increasingly positive ion- less repulsion.
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When do big jumps in IE occur?
When a new shell is broken into (stronger attraction as closer to nucleus) and when have lost enough electrons to have a noble gas configuration.
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Drop between groups 2 and 3 shows what?
Sub-shell structure - extra sub-shell increases distance and shielding.
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Drop between groups 5 and 6 shows what?
Electron repulsion and orbitals - repulsion in shared orbital reduces IE.
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Atomic size does what as you move across a period?
Decreases - increased nuclear charge = attraction increases which pulls electron shells towards nucleus.
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Atomic size does what when you move down a group?
Increases - extra electron shell added.
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Atomic radius of isotopes are...
The same because they have the same no. protons and electrons - attraction pull = the same.
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Other cards in this set

Card 2

Front

Rutherford

Back

Positive alpha particles at sheet of gold. Most passed through, some deflected backwards. Concluded tiny, positive nucleus, electron 'cloud' and mostly empty space.

Card 3

Front

Bohr's Model

Back

Preview of the front of card 3

Card 4

Front

Quantum Model.

Back

Preview of the front of card 4

Card 5

Front

Relative Atomic Mass

Back

Preview of the front of card 5
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