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QLDChemistryQuick questions
Unit 1: Chemical fundamentals (structure, properties and reactions)
Quick questions on Atomic structure, isotopes and relative atomic mass (QCE Chemistry Unit 1)
8short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What are isotopes?Show answer
Isotopes of an element have the same number of protons but different numbers of neutrons, so the same atomic number Z but different mass number A.
What is mass spectrometry?Show answer
A mass spectrometer ionises a sample (usually by electron impact, knocking out one electron to form a singly charged cation), accelerates the ions through an electric field, separates them by mass-to-charge ratio (m/z) in a magnetic field, and detects each beam. The output is a mass spectrum: a plot of relative abundance against m/z.
What is calculating relative atomic mass?Show answer
The relative atomic mass (Ar) is the weighted mean of the isotopic masses by their natural abundance:
What is worked example: chlorine?Show answer
Cl-35 (mass 34.97, abundance 75.78 percent), Cl-37 (mass 36.97, abundance 24.22 percent).
What is worked example: magnesium from a mass spectrum?Show answer
Peaks at 24, 25, 26 with heights 79, 10, 11.
What is q1?Show answer
Explain the difference between the mass number and the relative atomic mass of an element. [3 marks]
What is q2?Show answer
Chlorine from Townsville seawater shows two peaks: at and at . Calculate to two decimal places. [3 marks]
What is q3?Show answer
A neutral atom has protons and a mass number of . (a) Write the standard isotope notation. (b) Give the electron configuration.