DP Chemistry (first assessment 2025)

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Question 19N.1A.SL.TZ0.5

Date	November 2019	Marks available	[Maximum mark: 1]	Reference code	19N.1A.SL.TZ0.5
Level	SL	Paper	1A	Time zone	TZ0
Command term	State	Question number	5	Adapted from	N/A

5.

[Maximum mark: 1]

19N.1A.SL.TZ0.5

What is represented by A in ${}_{\text{Z}}^{\text{A}}{{\text{X}}^{2 - }}$ ?

A. Number of electrons

B. Number of neutrons

C. Number of nucleons

D. Number of protons

[1]

Markscheme

C

Syllabus sections

Structure 1. Models of the particulate nature of matter » Structure 1.2—The nuclear atom » Structure 1.2.1 - Atoms and negatively charged electrons. Atoms contain a positively charged, dense nucleus composed of protons and neutrons (nucleons). Negatively charged electrons occupy the space outside the nucleus. Use the nuclear symbol ZXA to deduce the number of protons, neutrons and electrons in atoms and ions.