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chemistry > 1.1 - atomic structure * > Flashcards

1.1 - atomic structure * Flashcards

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1
Q

isotopes?

A
  • atoms with same number of protons but different number of neutrons.
  • similar chemical properties because they have the same electronic structure
  • varying physical properties because they have different masses
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2
Q

relative mass of an electron?

A

1/1840

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3
Q

what does a mass spectrometer do?

A
  • determine all the
    isotopes present in a sample of
    an element and to therefore
    identify elements
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4
Q

why does a mass spectrometer need to be under a vacuum?

A
  • otherwise air particles would ionise and register on the detector
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5
Q

what are the 3 steps in a mass spectrometer?

A
  1. ionisation
  2. acceleration
  3. detection
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6
Q

what is electron impact ionisation used for?

A
  • elements and substances with low formula mass as it can cause larger organic
    molecules to fragment
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7
Q

stages of electron impact ionisation?

A
  • a vaporised sample is injected at low pressure
  • an electron gun fires high energy electrons at the sample
  • this knocks out an outer electron
  • forming positive ions with different charges
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8
Q

what is electrospray ionisation used for?

A
  • for larger organic
    molecules as the softer conditions of this technique mean
    fragmentation does not occur
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9
Q

stages of electrospray ionisation?

A
  • sample dissolved in volatile solvent + injected through hypodermic needle
  • tip of needle attached to positive terminal of high voltage power supply
  • particles gain H+ ion
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10
Q

what happens in the acceleration stage?

A
  • positive ions are accelerated by an electric field to a constant kinetic energy
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11
Q

how to calculate mass of an ion in KG?

A

mass number/ 1000/ 6.022 x 10(23)

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12
Q

what happens in the detection stage?

A
  • sample attached to negative plate
  • current is generated that is proportional to the abundance
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13
Q

what is the kinetic energy equation?

A

KE = 1/2 x mass x (velocity)2

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14
Q

velocity equation?

A

distance/time

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15
Q

definition for relative atomic mass?

A

average mass of an atom of an element relative to 1/12th the mass of a C12 atom

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16
Q

equation for relative atomic mass?

A

mass of isotope x percentage abundance / 100

17
Q

how many electrons can each sub energy level hold?

A

s = 2
p = 6
d = 10
f = 14

18
Q

order of sub shells in electron configuration?

A

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p

19
Q

which sub shell is the anomaly and gets filled before which other sub shell?

A

4s gets filled before 3d

20
Q

why is chromium an exception to electron configuration?

A

the electrons only HALF fill 4s and 3d

21
Q

why is copper an exception to electron configuration?

A

3d is filled fully but 4s is only HALF filled

22
Q

definition of first ionisation energy?

A
  • the enthalpy change when one mole of gaseous
    atoms forms one mole of gaseous ions with a single positive charge
  • represented by equation:
    H (g) –> H+ (g) + e-
23
Q

definition of second ionisation energy?

A
  • the enthalpy change when one mole of gaseous ions with a single positive charge forms one mole of gaseous ions with a double positive charge
  • represented by equation:
    Ti+ (g) –> Ti2+ (g) + e-
24
Q

factors that affect ionisation energy?

A
  1. attraction of the nucleus
    (the more protons in the nucleus the greater the attraction)
  2. distance of the electrons from the nucleus
    (the bigger the atom the further the outer electrons are from the nucleus and the
    weaker the attraction to the nucleus)
  3. Shielding of the attraction of the nucleus (an electron in an outer shell is repelled by electrons in complete inner shells, weakening the attraction of the nucleus)
25
Q

why are successive ionisation energies always larger?

A
  • the second ionisation energy of an element is always bigger than the first ionisation energy
  • as when the first electron is removed a positive ion is formed
  • the ion increases the attraction on the remaining electrons and so the energy required to remove the next electron is larger
26
Q

how to tell what group an element is in based off ionisation energies?

A

eg: if there is a big jump between the 2nd and 3rd
ionisations energies then this
element must be in group 2 of the periodic table as the 3rd electron is removed from an electron shell closer to the nucleus with less shielding and
so has a larger ionisation energy

27
Q

why does helium have the largest first ionisation energy?

A
  • its first electron is in the first shell closest to the nucleus and has no shielding effects from inner shells
  • helium has a bigger first ionisation energy than H as it has one more proton
28
Q

why do first ionisation energies decrease down a group?

A

as one goes down a group, the outer electrons are found in shells further from the nucleus and are more shielded so the attraction of the nucleus becomes smaller

29
Q

why is there a general increase in first ionisation energy across a period?

A
  • as you go across a period the electrons are being added to the same shell which has the same distance from the nucleus and same shielding
    effect
  • the number of protons increases but makes the effective attraction of the nucleus greater
30
Q

draw graph of first ionisation energies for first 20 elements?

A

see google or physical flashcard for graph

31
Q

why does Na have a much lower first ionisation energy than Ne?

A
  • Na will have its outer electron in a 3s shell further from
    the nucleus and is more shielded
  • so Na’s outer electron is easier to remove and has a lower ionisation energy
32
Q

why is there a small drop from Mg to Al?

A
  • Al is starting to fill a 3p sub shell but Mg has its outer electrons in the 3s
    sub shell
  • the electrons in the 3p subshell are slightly easier to remove because the 3p electrons are higher in energy and are also slightly shielded by the 3s electrons
33
Q

why is there a small drop from P to S?

A
  • with sulphur there are 4 electrons in the 3p sub shell and the 4th is starting to doubly fill the first 3p orbital
  • when the second electron is added to a 3p orbital there is a slight repulsion between
    the two negatively charged electrons which makes the second electron easier to remove
34
Q

describe graph for second ionisation energies?

A
  • each successive element is plotted then a similar pattern to the first ionisation energy is observed but all the elements will have shifted one to the left
  • the group 1 elements are now at the peaks of the graph
  • Li would now have the second largest ionisation of all elements as its second electron would be removed from the first 1s shell closest to the nucleus and has no shielding effects from inner shells so Li has a bigger second ionisation energy than He as it has more protons
35
Q

draw graph for second ionisation energies?

A

see google or physical flashcard

chemistry (5 decks)

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