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24 Cards in this Set
- Front
- Back
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Relative mass and charge of protons, neutrons and electrons |
Protons: Relative Mass - 1 Charge - +1
Neutrons: Relative Mass - 1 Charge - none
Electrons: Relative Mass - 1/1840 Charge - -1 |
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Define: relative atomic mass (ar) |
Average mass of an atom of an element on a scale when an atom of carbon 12 is 12 |
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Define: relative molecular mass (mr) |
The average mass of a molecule on a scale where an atom of carbon-12 is 12 |
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Define: isotope |
An atom with the same number of protons as another atoms but a different number of neutrons |
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Define: relative isotopic mass |
The mass of an isotope, of an atom of an element, on a scale where an atom of carbon-12 is exactly 12. |
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How did the atomic model develop into what it is today? |
1) Dalton's & Thomson's model Atoms are solid spheres, different spheres = different atoms Thomsons concluded atoms contain neg- particle-> electron. Plum pudding model created. 2) Rutherford Gold foil experiment-> atoms are mostly empty, w/pos+ nucleus in centre. 3) Bohr Shells have fixed energy When electrons move between shells, electromagnetic radiation emitted/absorbed. 4) Bohr Refined Not all electrons in a shell have a fixed energy 5) Other Based on quantum mechanics, explains more but is harder to visual. Use which ever is easiest. |
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Relative atomic mass calculation |
(Isotopic masses × percentages) + (isotopic masses × percentages ) ÷ Total percentage |
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TOF:MS - Stage 1 |
Ionisation - • Electrospray Sample dissolved in volatile solvent Pushed through small nozzle at high pressure High voltage applied Each particle gains proton (becomes isotope) Solvent removed
• Electron impact Sample vaporised 'Electron gun' fires high energy electrons at atoms Usually knocks off an electron (Fragmentation usually occurs) |
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TOF:MS - Stage 2 |
Acceleration - Ions accelerated by electric field (provides same kinetic energy to all ions) Lighter ions have greater acceleration. Same kinetic energy but they're lighter, accelerate more |
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TOF:MS - Stage 3 |
Ion Drift - Ions enter region without an electric field Drift through at same speed as they left the field Lighter ions drift at high speeds |
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TOF:MS - Stage 4 |
Detection - Lighter ions reach detector in less time than heavier ones. Detects current created, when ions hit, and time taken to pass through TOF:MS |
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What is mass spectra? |
The chart created after detection. The height of the peak provides the relative isotopic abundance.
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Whats the electronic structure of atoms? |
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Whats the electronic configuration of copper? (Ar = 29) |
1s[2], 2s[2], 2p[6], 3s[2], 3p[6], 3d[10], 4s[1] |
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What's the electronic configuration of chromium? (Ar = 24) |
1s[2], 2s[2], 2p[6], 3s[2], 3p[6], 3d[5], 4s[1] |
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What happens to the electronic configuration of an atom when it is a pos+ ion? |
Remove an electron from orbital. |
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What happens to the electronic configuration of an atom when it is a neg- ion? |
Add an electron onto orbital. |
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Define: first ionisation energy |
The energy needed to remove one mole of electrons from one mole of atoms to form one moles of positive ions, in a gaseous state |
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What is the unit for ionisation energy? |
KJ mol[-1] |
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What are the equations for the successive ionisation energies of sodium? |
Na(g) -> Na+(g) + e- Na+(g) -> Na 2+(g) + e- |
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Complete: The lower the ionisation energy... |
... the easier is it to remove an electron to form an ion |
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What are the 3 factors affecting ionisation energy? |
• Distance from nucleus Electrons closer to the positively charged nucleus Strongly attracted • Nuclear Charge More protons in nucleus More positively charged the nucleus Stronger attraction • Shielding Inner shell electrons repel outer shell electrons Lessens the pull toward the nucleus |
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What happens to ionisation energies across a period? (General trend, dips) |
General trend - Ionisation energy increases. More protons = stronger nuclear attraction
Dips - Between Mg (group 2) and Al (group 3) •Aluminium has outer electrons in 3p, not 3s Electrons further from nucleus than Magnesiums. •3p has shielding from 3s orbital. Between P (group 5) and S (group 6) • Similar shielding Sulphur electron removed from orbital with 2 electrons Easier to remove bc of repulsion. |
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What happens to ionisation energy across a group? Why? |
Decreases down a group. Each element has 1 more electron shell= Shielding occurs. Further from nucleus. Reduced nuclear attraction. |
