Before you read this, I suggest you read post 25.3. I briefly introduced the idea of a resonance hybrid in post 16.31. Since then, I’ve written a lot about resonance, especially in post 18.8. Unfortunately, understanding resonance won’t help you to understand resonance hybrids. Resonance is not involved in the concept of resonance hybrids. I… Continue reading 25.4 Resonance hybrids
Before you read this, I suggest you read post 25.2. The formula of benzene is often written as shown in the picture above. The molecule shown here is a ring of six carbon atoms joined by alternating single and double covalent bonds. There is also a hydrogen atom bonded to each carbon atom. This structure… Continue reading 25.3 Benzene molecule
Before you read this, I suggest you read post 25.1. In post 25.1, I started to describe how the valence bond theory explains how carbon and hydrogen atoms are joined in molecules of ethane, ethene and ethyne (see picture above). My purpose was to introduce the concept of hybrid orbitals. In this post, I am… Continue reading 25.2 Sigma bonds and pi bonds
Before you read this, I suggest you read posts 16.30 and 24.12. I am going to use the bonding in molecules of ethane, ethene and ethyne (see the picture above) to introduce the concept of hybrid orbitals. In post 16.31, we saw that, according to the valence bond theory, a molecule consists of atoms held… Continue reading 25.1 Hybrid orbitals
In post 16.29, we saw that the lowest energy levels in an atom are conventionally labelled, in order of increasing energy, 1s, 2s and 2p. There are three 2p levels that all correspond to the same energy; they are denoted 2px, 2py, and 2pz. Electrons occupy these energy levels according to the principles explained in… Continue reading 24.12 Atomic orbitals
I have written about the first, second and third laws of thermodynamics; these three laws are numbered in chronological order and, I believe, in logical order. But, in 1932, the English physicist Sir Ralph Fowler (1889-1944) proposed that there should be a further law that logically belonged before the other three. So it is called… Continue reading 24.11 Zeroth law of thermodynamics
A more accurate description of this post would be, seeking a single, simple cause for the combined effect of many factors. But this would be a very cumbersome heading. Let’s look at an everyday example: a man is depressed after his wife leaves him. His friends believe he is depressed because his wife left him.… Continue reading 24.10 Multifactorial problems – seeking a cause that doesn’t exist
This post is about how organic chemistry and biochemistry got their names. The Swedish chemist Jöns Berzelius (1807-1882) appears to have introduced the name “organic chemistry” for the study of molecules derived from living things. This appears to imply that living stuff is different to non-living stuff. In post 16.18, I explain my reasons for… Continue reading 24.9 Organic chemistry and biochemistry
You step on your bathroom scales to find your body mass. The idea is that gravity acts on your mass to exert a force that depresses a platform. The depression of the platform depends on the force and, hence, on your body mass. So, to find your body mass, you need to measure the depression… Continue reading 24.8 Passive damping – bathroom scales
Before you read this, I suggest you read posts 24.5 and 24.6. In post 21.1 we saw that an electrical circuit that consists only of a capacitor discharging through an inductor is a simple harmonic oscillator in which the charge, Q, depends on time, t, according to the equation Q = Q0eiωt (1) (equation B4… Continue reading 24.7 Driven oscillator
Thinking about Science with David Hukins 