Question 23M.3.HL.TZ1.1
| Date | May 2023 | Marks available | [Maximum mark: 8] | Reference code | 23M.3.HL.TZ1.1 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Explain, Outline, Sketch, Suggest | Question number | 1 | Adapted from | N/A |
Graphs showing the first ionization energy and first electron affinity of the elements in period 2 of the periodic table are shown.
[Source: Wikipedia, n.d. Electron affinity. [online] Available at: https://en.wikipedia.org/wiki/Electron_affinity
[Accessed 22 June 2021]. Source adapted.]
Outline why ionization energies have positive values but most electron affinities have negative values
[1]
ionization energy breaks bond/attractive force between nucleus and electron
AND
electron affinity forms bond/attractive force between nucleus and electron ✓
Accept for ionization energy “energy needed/endothermic to remove an electron".
AND
for electron affinity “energy released/exothermic adding an electron”.
First ionization energy tends to increase across the period. Explain the decrease in first ionization energy from beryllium to boron.
[2]
electron «removed» from 2p in B AND 2s in Be ✓
shielding effect of 2s «reduces energy needed to remove 2p»
OR
2p at higher energy level/further from nucleus
OR
full 2s more stable «than single electron in p» ✓
Accept electron configurations of both B and Be for M1.
The electron affinity of nitrogen is 6.8 kJ mol−1. Sketch the 2s and 2p orbital filling diagram that represents the electron arrangement of the species produced.
[1]
Accept second arrow, representing opposite spin, in any 2p box.
Accept half-arrows.
Suggest one reason for a positive value for the first electron affinity for nitrogen.
[1]
greater repulsion when electrons occupy same orbital ✓
Accept electron added to stable half-filled p sublevel.
Suggest reasons why noble gases have the largest first ionization energy and largest positive first electron affinity in their period.
Largest first ionization energy: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Largest positive first electron affinity: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[2]
Largest first ionization energy:
highest nuclear charge «for a similar radius/same energy level»
OR
smallest radius
OR
stable octet ✓
Largest positive first electron affinity:
adding to new principal energy level
OR
«much» further from nucleus
OR
shielded by completed inner shell ✓
Do not accept “complete octet” without reference to stability for M1.
Suggest, giving one reason, how the first electron affinity of xenon compares with that of neon.
[1]
ALTERNATIVE 1:
«Xe» lower/smaller/less positive AND larger radius
OR
«Xe» lower/smaller/less positive AND smaller energy gap to next «principal» energy level ✓
ALTERNATIVE 2:
«Xe» greater AND very high nuclear charge
OR
«Xe » greater AND poor shielding by inner «d» orbitals ✓
Accept converse arguments for either alternative only if it is clear that Ne being referred to.