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EDEXCEL Chemistry a level > Atomic structure and the periodic table > Flashcards

Atomic structure and the periodic table Flashcards

Fundamental particles Mass spectrometry Ionisation energies Electronic configurations Periodicity

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1
Q

RELATIVE ATOMIC MASS

A

The weighted mean mass of an element, compared to 1/12th the mass of an atom of carbon 12.

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2
Q

RELATIVE ISOTOPIC MASS

A

the mass of an atom of an isotope of the element compared to 1/12th the mass of C12.

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3
Q

mass spectrometry

A

Allows calculation of exact relative masses of isotopes from a mass spectrum of element and percentage abundances.

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4
Q

How’s the relative molecular mass of a covalent compound obtained from a mass spectrum?

A

The highest value of mass to charge (m/z) (molecular ion peak) is identified as a peak and therefore corresponds with the relative molecular mass of the covalent compound.

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5
Q

2 forms of spectrometry?

A

electron impact

electrospray

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6
Q

electron impact spectrometry uses?

A

elements and low Mr compounds

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7
Q

electron impact method

A

high energy electrons are fired at the sample from an electron gun to knock off electrons and form ions.

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8
Q

equation for electron impact ionisation

A

X(g)&raquo_space; X+(g) + e-

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9
Q

electrospray uses

A

high Mr compounds

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10
Q

electrospray method

A

The sample is dissolved in a volatile solvent and injected via a fine hypodermic needle as a spray into a vacuum of an ionisation chamber with a high voltage at the end of the needle which has a positive charge.

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11
Q

what occurs after ionisation in spectrometry?

A

ion acceleration via an electric field so all ions have the same kinetic energy

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12
Q

what occurs after ion acceleration in spectrometry?

A

the charged ions are separated. Drifting as they enter the flight tube, those of different masses will have different flight times.

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13
Q

How are the ions detected in spectrometry?

A

a negative detector plate produces a current when ions hit them, in which more ions create a larger current. time of flight and the current produced allows determination of relative abundance and mass per charge.

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14
Q

why is ionisation necessary in spectrometry?

A

so that the ions may be accelerated within the electrical field and allowing detection of mass per charge when the ions produce a current on the negative detector plate.

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15
Q

How are ions accelerated, detected and have their abundance determined in a TOF mass spectrometer?

A

The ions are accelerated within a vacuum vua the presence of an electric field, causing the ions to drift down the flight tube, attracted to the detector plate which produces a current when electrons are absorbed. The time of flighta nd mass per charge can enable the calculation of abundance and mass.

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16
Q

what’s on the x and y axis of a mass spectrum?

A

x is m/z (mass to charge)

y is relative abundance of ions (%)

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17
Q

equation for flight time of ions in chamber

A

t=d(square root of

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18
Q

Number of subshells within each quantum shell

A

1 (one subshell) 1s 2
2 (two subshells) 2s, 2p 8
3 (three subshells) 3s, 3p, 3d 18
4 (4 subshells) 4s, 4p, 4d, 4f 32

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19
Q

S orbital
Shape?
Number of electrons?
Where located on periodic table?

A

Circular orbital made up of 2 electrons.

Sz Sy Sx

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20
Q

P orbitals

A

Dumbbell shape holding 6 electrons and a variable charge density.
Px Py Pz

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21
Q

D orbital

A

Double dumbbell shape holding 10 electrons.

Dxy Dxz Dyz Dx(squared)-y(squared) Dz(squared)

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22
Q

Orbital

A

A region within an atom that can hold up to two electrons with opposite spins.

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23
Q

Aufbau principle

A

As protons are added to the nucleus, electrons are successively added to orbitals of more energy (starting w lowest) until all electrons are accommodated.

24
Q

Hund’s rule

A

Electrons occupy orbitals singly before pairing takes place.

25
Q

Pauli exclusión principle

A

No 2 electrons can occupy the same space unless they have opposite spins.

26
Q

Why is there exceptions to the aufbau principle?

A

Electrón-electron repulsión and number of protons in the nucleus.

27
Q

Evidence for quantum shells

A

Emission spectra

Ionisation energies

28
Q

Emission spectra

A

Gaseous atoms given energy via heating/electricity to push electrons to higher energy levels, upon return, EM radiation is emitted.
Analysis of radiation via a spectroscope provides an emission spectra.
Specific frequencies show quantised energies of electrons

29
Q

Ionisation energy

A

A measure of the energy required to completely remove an electron from an atom of an element.

30
Q

Trend in successive IE

A

First electron is easier to remove than 2nd and steady increase for next 8. Final 2 are harder to remove than previous 8.
Final 2 are located in first quantum shell (lowest energy)

31
Q

Why do successive IEs increase?

A

As electron lost is at infinite distance to nucleus so energy needs to be increased to a particular value for it to be released. Lower energy= higher IE

32
Q

Electron electron repulsion

A

Exists between 2 e- of same/different orbital within a given quantum shell or 2 adjacent quantum shells (most significant).

33
Q

Impacts on electron energies

A

Shielding/screening

Nuclear charge

34
Q

Shielding

A

Electron electron repulsion between adjacent shells increases energy of electrons and so lowers IE

35
Q

Charge

A

Higher charge due to more protons in the nucleus decreases the energy of electrons, increasing IE.

36
Q

Trends across a period

A

Nuclear charge increases as atomic number increases (decreasing energy and so increasing IE)
More electrons are added, adding to the electron electron repulsion, increasing e- energy and decreasing IE.
Nuclear charge outweighs effects of shielding,increasing IE across a period.

37
Q

Successive IE down a group

A

Nuclear charge increases as protons increase, decreasing electron energy and so increasing IE.
More quantum shells increase shielding and so decrease IE
Shielding overtakes charge impacts, decreasing IE overall

38
Q

Which groups do the trends in period/group occur in?

A

2 5 6 7 8
4 is anomaly as Pb has higher than tin
No trend in 3

39
Q

Periodicity

A

Regularly repeating pattern of atomic, physical and chemical properties w increasing atomic number.

40
Q

probability of finding electron within subshell boundary

A

90% chance

41
Q

number of orbitals in f subshell

A

7

therefore 14 electrons

42
Q

what determines the chemical properties of an element?

A

the number and arrangement of electrons

43
Q

what determines physical properties of an element?

A

the mass of the atom

44
Q

why do isotopes hold different physical properties to other atoms of the same element?

A

because it has a different mass

45
Q

why is RAM not usually a whole number

A

as is an average of relative isotopic masses (which are usually whole numbers)

46
Q

what’s relative molecular mass used for?

A

simple molecules

47
Q

what’s relative formula mass used for?

A

ionic or giant covalent compounds

48
Q

molecular ion

A

the molecule in which electrons are removed from when bombarded w electrons

49
Q

molecular ion peak

A

relative molecular mass of a compound w the highest mass per charge ratio, caused by the molecular ion

50
Q

S block

A

group 1 and 2

51
Q

Cr and Cu electronic configuration

A

donate one of their 4s electrons to the 3d subshell

52
Q

4s and 3d subshells difference

A

4s fill before the 3d

53
Q

first ionisation energy

A

energy required to remove one electron from every atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.

54
Q

what sort of process is ionisation

A

endothermic

55
Q

What happens to the melting and boiling points of metals across the period?

A

increase as metallic bonds grow stronger and radius decreases, meaning higher charge density

EDEXCEL Chemistry a level (12 decks)

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