Question 23M.3.HL.TZ2.1
| Date | May 2023 | Marks available | [Maximum mark: 7] | Reference code | 23M.3.HL.TZ2.1 |
| Level | HL | Paper | 3 | Time zone | TZ2 |
| Command term | Estimate, Explain, Outline, Suggest | Question number | 1 | Adapted from | N/A |
One definition of atomic volume is given by the formula:
The table gives the atomic volumes of the first nineteen elements, in the form in which they occur at STP.
Outline why many elements have atomic volumes greater than 10 000 cm3 mol−1.
[1]
gases «and others are solids» ✓
Do not accept “lower density” alone.
Outline why some of those with larger atomic volumes have values ~11 000 cm3 mol−1 and others ~22 000 cm3 mol−1.
[1]
smaller values are diatomic «gases»
OR
larger values are monatomic «gases» ✓
Accept “smaller values are species that exist as molecules”.
Do not accept answers referring only to noble gases or electron configurations.
Suggest why some elements, such as carbon and oxygen, have more than one value for their atomic volume.
[1]
«different» allotropes ✓
Accept “different structural forms” OR “oxygen forms different molecules”.
Accept correct formulas or names of allotropes.
Accept monatomic oxygen/O only if mentioned with respect to other allotropic form or explanation provided.
Do not accept “different isotopes” alone.
Explain why the atomic volumes of elements 11, 12 and 13 show a steady decrease.
[2]
Any two of:
increasing «effective» nuclear charge/Z/atomic number/number of protons ✓
increasing number of delocalized/bonding/valence electrons ✓
increasing attractions between positive «metal» ions/cations and delocalized electrons
OR
stronger metallic bonding
OR
decreasing radii ✓
Estimate the atomic volume, in cm3 mol−1, of element 20.
[1]
any estimated value in the range of 20-40 «cm3 mol−1». ✓
Accept any range of values also between 20 to 40 «cm3 mol−1».
Suggest, giving one reason, whether you could ever know the actual volume of a single atom.
[1]
no AND probability of finding an electron is low
OR
no AND all measurements have uncertainties «even though there will always be uncertainty as to what the exact value is»
OR
yes AND X-ray diffraction can indicate separation of nuclei «in the element»
OR
yes AND can take a sample of the element, measure its volume and calculate number of particles
OR
yes AND bond length can be measured by microwave spectroscopy/electron diffraction/neutron diffraction ✓
Accept “no AND position of electron cannot be determined” for M1.
Accept “no AND atoms made up of « mainly» empty space that cannot be measured” for M1.
Accept “no AND atoms have different volumes in different states «of matter»” for M1.
Accept “no AND the distance between two nuclei is measured and the radius/volume/size of atom is estimated” for M1.
Accept references to the Heisenberg uncertainty principle for M1.