DP Chemistry (first assessment 2025)

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Question 19M.1A.HL.TZ1.12

Date	May 2019	Marks available	[Maximum mark: 1]	Reference code	19M.1A.HL.TZ1.12
Level	HL	Paper	1A	Time zone	TZ1
Command term		Question number	12	Adapted from	N/A

12.

[Maximum mark: 1]

19M.1A.HL.TZ1.12

Which species has delocalized electrons?

A. OH⁻

B. H₂CO

C. CO₂

D. CO₃²⁻

[1]

Markscheme

D

Examiners report

This question on delocalized electrons was also well answered.

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.