An example of an analogy between a scientific concept and an everyday phenomenon in popular science writing*:
"It's the exchange of electrons that defines the need for chemical bonding: to join with other atoms in such a way that will create a more stable overall structure: a compound. Other than the the noble gases such as helium, very few atoms have the right number of electrons on their own to achieve peak stability. So they look for others to bond with, in ways that will complete them (aww).
In this, atoms are really no different from the people they ultimately create, looking for others to form connections with for a happier and, perhaps, easier life. And just like our human relationships, the way they come together varies. Sometimes there is a true meeting of minds, in the form of an electron being shared; others happen when one atom gives up an electron for the sake of another; still more are the product of the electrical charges created as electrons are traded.
I believe there are clear parallels between the different kinds of bonds atoms form, and the relationships we create in our own lives…The most mutual form of chemical bonding is covalent, whereby two or more atoms share electrons in order to complete their outer structures. Within the outer atomic shells, the magic number is eight, the requisite number of electrons to achieve stability – a state in which the electromagnetic push and pull between the nucleus and the electrons is minimised.
Hence atoms are engaged in a sort of chemical speed date to find the right partner or partners to fill their quota. Take one compound we are all breathing in right now: carbon dioxide or CO2. This comes about thorugh a single carbon atom of four electrons sharing two electrons each with two oxygens given them both a stable eight.
Covalent bonding is an exercise in stability through sharing – a collaborative effort to create a chemical balance where both (or all) partners need each other equally. These bonds reflect the relationships in our lives that are baed on common understanding and shared principles or values: where there is an innate symmetry that creates a long-lasting connections, and minimal drama or volatility. When you meet someone and feel like you've always known them, then you know how a covalent bond feels. …
Where covalency is about mutual dependency, ionic bonding relies more on give and take. Here, there is a transfer of electrons from one atom to another, creating an electrostatic charge that holds the atoms together.
In the case of another familiar everyday element [sic], sodium chloride or NaCl, this happens when sodium donates the single electron in its outermost shell to chlorine, which has started with seven. …
Ionic (or polar) bonds are those which are based on the attraction of difference. They are less about complementarity than the transfer of power. These are the relations in which you know the other person may be totally different from you, but there is an interest or attraction that unerringly draws you closer to them. Ionic bonds are stronger than their covalent cousins, taking more energy to break apart – i.e., they have a higher melting or boiling point. This means that although an ionic relationship might be more emotionally volatile, in chemical terms ionic bonds are actually more stable. This natural asymmetry reflects the balance of power in a friendship, which in a healthy relationship equalises over time through natural exchange and swapping."
Dr Camilla Pang
Pang, C. (2020). Explaining Humans. What science can teach us about life, love and relationships. Viking.
As well as developing an analogy between relationships and types of chemical bond, this extract uses simile (speed dating), metaphor (cousins, trading, magic number) and anthtropomorphism (suggesting atoms behave like sentient actors in the world, having intentions and feelings).
Read examples of scientific analogies
Read about examples of science similes
Read examples of anthropomorphism in science
* For a science teacher, there are a number of problems with the text quoted here. These include:
- Atoms themselves are usually inherently more stable as atoms than they would be if gaining or loosing electrons to give 'the magic number' of 8 (although compounds are more stable than the discrete elements).
- Ionic bonding does not involve electron transfer between atoms. (And ionic bonding involves ions not atoms.)
- Bonds do not have melting or boiling points (melting and boiling temperatures apply to samples of substances).
- Covalent bonds are usually stronger (more stable) than ionic bonds.
- Sodium choride is not an element, but a compound.
- The statement that "the electromagnetic push and pull between the nucleus and the electrons is minimised" in the covalently bonded state is confused and in error. There is ONLY 'pull' (attraction) between nuclei and electrons, and this will tend to be greater, not minimised, in the bonded state – in general, a more stable (lower energy) state will be due to stronger forces acting.
- The net force acting will be zero because the attractions are balanced by repulsions ('pushes'), but these are between the nuclei present; and between the electrons present. The molecule or lattice is in an equilibrium state, or it owuld not be stable.
- Ionic bonds and polar bonds are not the same things: many polar bonds are closer to being pure covalent than pure ionic.
- If one uses there 'sharing' metaphor for covalent bonding, then the bonding in carbon dioxide (which we indeed breathe in, but breathe out in much higher concentrations/partial pressures) involves "a single carbon atom of four [outer shell] electrons sharing two [pairs of] electrons each with two oxygens given them both a stable eight" as the covalent bond invovles a pair of electrons, and the double bond two pairs.
