DP Chemistry (first assessment 2025)

Test builder »

Question 19M.2.SL.TZ2.b(iii)

Select a Test
Date May 2019 Marks available [Maximum mark: 2] Reference code 19M.2.SL.TZ2.b(iii)
Level SL Paper 2 Time zone TZ2
Command term Predict Question number b(iii) Adapted from N/A
b(iii).
[Maximum mark: 2]
19M.2.SL.TZ2.b(iii)

Predict, giving two reasons, how the first ionization energy of 15N compares with that of 14N.

[2]

Markscheme

Any two:
same AND have same nuclear charge/number of protons/Zeff  [✔]

same AND neutrons do not affect attraction/ionization energy/Zeff
OR
same AND neutrons have no charge [✔]

same AND same attraction for «outer» electrons [✔]

same AND have same electronic configuration/shielding [✔]

 

Note: Accept “almost the same”.
“same” only needs to be stated once.

Examiners report

This was a challenging question for many candidates, while stronger candidates often showed clarity of thinking and were able to conclude that the ionization energies of the two isotopes must be the same and to provide two different reasons for this. Some candidates did realize that the ionization energies are similar but did not give the best reasons to support their answer. Many candidates thought the ionization energies would be different because the size of the nucleus was different. Some teachers commented that the question was difficult while others liked it because it made students apply their knowledge in an unfamiliar situation. The question had a good discrimination index.

Syllabus sections