DP Chemistry (first assessment 2025)
Question 19M.1A.SL.TZ2.11
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.1A.SL.TZ2.11 |
| Level | SL | Paper | 1A | Time zone | TZ2 |
| Command term | Question number | 11 | Adapted from | N/A |
11.
[Maximum mark: 1]
19M.1A.SL.TZ2.11
Which molecule contains an incomplete octet of electrons?
A. NF3
B. BF3
C. BrF
D. SF2
[1]
Markscheme
B
Examiners report
66 % of the candidates identified BF3 as having an incomplete octet of electrons. The distractors NF3 and BrF were chosen in equal numbers, and the distractor SF2 was chosen by the least number of candidates.
Syllabus sections
Structure 2. Models of bonding and structure » Structure 2.2—The covalent model » Structure 2.2.1—A covalent bond is formed by the electrostatic attraction between a shared pair of electrons and the positively charged nuclei. The octet rule refers to the tendency of atoms to gain a valence shell with a total of 8 electrons. Deduce the Lewis formula of molecules and ions for up to four electron pairs on each atom.