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VICChemistryQuick questions
Unit 1: How can the diversity of materials be explained?
Quick questions on Atoms, isotopes and mass spectrometry: VCE Chemistry Unit 1
10short 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 is the nuclear model?Show answer
An atom has a tiny, dense nucleus containing protons (positive) and neutrons (neutral), surrounded by electrons (negative) in shells. The nucleus holds almost all the mass; the electrons occupy almost all the volume.
What is nuclear notation?Show answer
An atom is written as ^A_Z X, for example ^12_6 C for carbon-12. Reading it: Z = 6 protons, A = 12 nucleons, so 6 neutrons and (in a neutral atom) 6 electrons.
What is isotopes?Show answer
Isotopes are atoms of the same element (same Z) with different mass numbers (different numbers of neutrons). Examples:
What is relative isotopic mass and relative atomic mass?Show answer
The relative isotopic mass of an isotope is its mass relative to one-twelfth the mass of a ^12_6 C atom. By definition, ^12_6 C has a relative isotopic mass of exactly 12.
What is mass spectrometry?Show answer
A mass spectrometer separates ions by mass-to-charge ratio (m/z). The simplified workflow:
What is confusing mass number with relative atomic mass?Show answer
Mass number is an integer (protons + neutrons) for a single isotope. Relative atomic mass is the weighted mean across all isotopes and is rarely a whole number (Cl is 35.45, not 35 or 36).
What is forgetting to divide percentages by 100?Show answer
If abundances are given as 75.78% and 24.22%, use 0.7578 and 0.2422, or divide the final answer by 100. Doing neither inflates the answer by 100x.
What is adding electrons to the mass?Show answer
Electrons are about 1/1836 the mass of a proton. For VCE you treat their contribution as zero. The relative isotopic mass is set by protons + neutrons.
What is calling isotopes different elements?Show answer
Isotopes share the same Z (same number of protons) and therefore the same element identity. Only the neutron count changes.
What is misreading the y-axis as the mass?Show answer
The y-axis of a mass spectrum is relative abundance. The mass (or m/z) is on the x-axis.