![]() ![]() In either event, the factual recall of niobium being in group 5 is a necessary condition for getting the answer. To solve this problem, a student needs to use either the ionic or the neutral scheme of counting to work out that the complex has 17 valence electrons. Give the organometallic electron count of NbCp2(H)(Et) I still tell my students to learn the f-block elements because the examiners are entitled to withhold the sequence. In fairness to recent examiners, the lanthanide sequence is sometimes given by doing something like labelling the x-axis of a graph. Is this a question about Hund’s Rules, or is it one about knowing where holmium is? At the moment, it’s both. As 10 is larger than 7, J will be the sum of S and L (rather than the difference between them). To get this question right, the student needs to extract the correct values of S and L from the configuration of 10 f-electrons associated with the ion. State the ground state multiplet symbol (2S+1)L(J) of Ho3+. Should their mark be docked because they mis-remembered which group cobalt is in? How big a penalty should recall activities incur here when the process knowledge is all in place? Lanthanide Multiplet Symbols But what mark should a correct analysis of the wrong electron count attract? The student has shown they can do the substantive science - this is the higher-order thinking. If students get the right number at the end, they have demonstrated that they can do all of this. To solve this problem you need to populate the tetrahedral splitting diagram with the correct number of electrons, and then apply the spin-only formula to convert the number of unpaired electrons into a magnetic moment. If students get the question right, they have demonstrated all of this, but what if they mis-remember? An incorrect count gives an incorrect answer. ![]() ![]() The VSEPR analysis requires a correct electron count, and a correct electron count requires the student to recall that tin is in group 4. This style of question is common in first year exams, and related problems often appear in point group and NMR problems at later stages. This gives you a trigonal bipyramidal (D3h) structure. To solve this problem, you need to count the number of electrons around tin and select the appropriate VSEPR shape. How many marks can someone access at Oxford if they can do chemistry but can’t remember the periodic table? Representative Exam Questions VSEPR I am going to analyse a few representative exam questions to try and explore what role memorisation of the periodic table plays in current assessments. If memorisation isn’t really what we want students to do, then our assessments should reflect that, focusing instead on the ideas and arguments woven through advanced chemistry. In all three of these outlooks, memorisation is probably not the point of a University education: memorisation shouldn’t be too central in the work students need to do to get a degree (though there probably are some facts which it is convenient to memorise). By this view there is perhaps a sophistication to a graduate chemist which a school-leaver develops during a degree. Perhaps you knew that water was v-shaped at school because of the two lone pairs, but now you think about the bending of water in terms of a Walsh diagram and the stabilisation of the HOMO through the s-p mixing permitted in the C2v point group. Some people appeal to a vaguer notion of Higher Education being about coming into a relationship with disciplinary knowledge. This perspective often draws the focus to specific verbs (to synthesise information is a higher order of learning than to comprehend it). Some people appeal to the level of cognition (perhaps memorising “electronegativity is the ability of one atom to pull electron density towards itself in a covalent bond” is lower-order than interpreting the orbital coefficients of the MO diagram of HF). This perspective often draws the focus to specific concepts. Some people appeal to the advanced content of study (perhaps the octet rule is lower-order education than MO theory). What effect does this have on assessment validity? This blog explores how a series of representative exam questions are problematic in light of the memorisation requirement. Oxford’s chemistry degree requires students to memorise the periodic table (not the mass numbers, but the positions of all the elements).
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