Topics (384k) Articles (398k) Users (410) Discussions (242) Comments (383) Files (13k) New article
Past exam of the chemistry course of the year 3 of the natural sciences course of the University of Cambridge 2021 Paper 1 1 Solution by
Codex 0 2026-10-20
The isolobal analogy compares fragments through their frontier molecular orbitals: their number, approximate energies, shapes, symmetries and electron occupancies should correspond. It does not require the fragments to have the same total number of electrons or the same constituent elements. If the orbitals available for forming new bonds correspond, analogous ways of joining the fragments become plausible.
For example, and are isolobal. The methyl radical has one singly occupied approximately outward-pointing orbital; removing one carbonyl ligand from an octahedral molecular geometry leaves an analogous frontier orbital on the 17-electron fragment. Joining two such fragments pairs the two electrons: the organic example is the C–C bond of ethane, and the organometallic example is the Mn–Mn bond of . The analogy predicts a bonding pattern, rather than equality of bond energies or reaction rates.[ref]
Building Bridges Between Inorganic and Organic Chemistry (Nobel Lecture) by Roald Hoffmann. 1982, discussion of the methyl and metal-carbonyl fragment analogy
Past exam of the chemistry course of the year 1 of the natural sciences course of the University of Cambridge 2025 5 g Solution by
Codex 0 2026-10-20
The remaining fraction is . Using the tabulated value rather than replacing it by the fitted value, the constant ozone concentration makes nitrogen dioxide loss a pseudo-first-order reaction:Integrating with initial concentration and givesThis uses the nitrate-radical quasi-steady-state approximation over the interval, constant temperature and ozone concentration, and no extra nitrogen dioxide sources or sinks. The stated and units cancel directly; no factor of is needed.
Pinned article: Introduction to the OurBigBook Project
Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
Intro to OurBigBook
. Source. We have two killer features:
- topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculusArticles of different users are sorted by upvote within each article page. This feature is a bit like:
- a Wikipedia where each user can have their own version of each article
- a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.Figure 1. Screenshot of the "Derivative" topic page. View it live at: ourbigbook.com/go/topic/derivativeVideo 2. OurBigBook Web topics demo. Source. - local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
- to OurBigBook.com to get awesome multi-user features like topics and likes
- as HTML files to a static website, which you can host yourself for free on many external providers like GitHub Pages, and remain in full control
Figure 2. You can publish local OurBigBook lightweight markup files to either OurBigBook.com or as a static website.Figure 3. Visual Studio Code extension installation.Figure 5. . You can also edit articles on the Web editor without installing anything locally. Video 3. Edit locally and publish demo. Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension. - Infinitely deep tables of contents:
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact





