How do you think of chemicals? I view them as arrangements of matter particles that are themselves composed of energy; they are arrangements of energy nodes if you like. Particle energy nodes have energy desires and consequently absorb and emit photon energies. All structures from the smallest atom to the largest object in our universe are composed of energy exchanging particle energies. The particles in structures are always seeking to get their energy needs in the most energy efficient way. If there are energy savings to be made and if the circumstances are right they will chemically combine with other structures to that end.
In chemistry we learn about electrons, protons and neutrons. We learn of their arrangements in atomic elements and in molecules, mixtures and compounds. We discover states of matter, ions, isotopes and covalent, ionic and metallic bonds. We are introduced to chemical equations and learn how to balance them in terms of atoms, volumes and masses. Rarely do we hear that atomic particles seek to satisfy their energy desires in a way that uses least energy. Yet it is the fundamental reason why chemical changes occur. Chemical change is all about particles reacting to the energies of their surround environment and forming structures that more efficiently satisfy their energy desires in that environment.
If we ask why hydrogen and oxygen exist as the molecules H2 and O2 we are told they are more stable. But what is this stability? It is the result of particles coming together in more energy efficient, energy exchanging structures. There is less total energy (node energy and photon energy) and therefore marginally less mass in the molecule than in the two separated atoms. The atom particles combine as a molecule because together they use less energy satisfying their energy desires.
For some reason particles pro actively desire energy and want to get it in the most efficient way. Such desires for energy are the reason for light speed photon energy flows and the associated particle energy absorptions and emissions. Those same desires are what hold the particles of a structure at a distance and cause them to vibrate.
Water H2O is a more energy efficient combination of hydrogen and oxygen. We use this fact in fuel cells to harvest electrical energy. Simply bringing oxygen and hydrogen together in the right proportions in a container will not of itself create water and release energy because the molecules in the mixture are content with their energy interactions. However, if we input a spark of photon energy we upset that particle contentment and some re-combine as water, releasing photon energy. That photon energy further upsets the contentment and a rapid explosive energy releasing change to water ensues.
The burning of paper, wood, domestic gas and fuel in car engines are other examples where an activation energy is required to trigger chemical changes that release heat in the process of forming more energy efficient structures of particles. Chemistry is an extensive subject but I hope in giving you the above few examples I have started to persuaded you that chemistry is really a science of preferred energy formations. We will return to this later but now let us consider changes of state.
Whilst chemical changes are about combining particle structures in more energy saving ways changes of state (solid, liquid, gas and plasma) are ways in which the same particle content can accommodate more or less energy. One change of state we are all familiar with involves ice, water and steam.
In the depths of winter photon energies from the sun and therefore passing between earth objects are reduced. The energy collecting electrons in water consequently move marginally closer to energy desiring nucleons making the water slightly less fluid (more viscous). Some movement or impurity in the water triggers a change to the less energy consuming but more rigid structure that is ice. The change releases photon energies. Ice is unusual because although its molecules are denser than those of water the way they link together in ice is more space consuming. It is why solid ice floats on water.
Input photon energy to ice and it will melt back to a water structure that can better and more efficiently accommodate the increased energy. Continue adding heat and that water will eventually turn to its vapour form steam. The diagram below shows energy is absorbed as ice changes to water and water to steam. The reverse processes of condensing and freezing give up energy.
A thermometer cannot enter a solid structure or the molecules of a liquid or gas structure. It responds to the photon energies outside of the solid or passing between fluid molecules. During a change of state there are substantial changes in mass energy yet temperature remains steady. Added energy goes to either expand the structure of solids or in the case of liquid and gas molecules both expand them and their distance apart. The looser energy links between liquid molecules and even looser energy links between gas molecules are why a hand movement can part them but not solids.
Temperature and heat content are clearly not related. Particle structures vary considerably and with it their ability to accommodate thermal energies when at the same temperature. Look up and compare the specific heat and thermal conductivity for several different material structures and you will see that some structures are far better than others at holding heat and some are better at conducting heat. Compare hot sand with cold sea or observe how some oven feel hotter than others.
It might appear that the flow of thermal energy along a structure is temperature driven from hot to cold but that is not how it is. The “hot” particles emit more than “cold” ones and “cold ones” absorb more than “hot” ones so that heat is dissipated in a hot to cold direction rather than temperature driven. We might, for example view the sun as being all energy output and no energy input, but its particle desires that pull photons from space into it maintain its spherical shape. Moreover the desires of its core particles deliver and control its mass energy releasing fusion process. Similarly the gravity desires of earth’s core particles contribute to the heat at its centre.
In chemistry it is not uncommon now to be introduced to reactivity diagrams like that shown for metals. The diagram enables us to say that iron added to copper sulphate will replace the copper and make for iron sulphate and that magnesium added to zinc chloride will replace the zinc and create magnesium chloride. The diagram also enables us to say that the reverse reactions will not naturally occur.
Rarely are we told why the reactivity series works. It works because the particles of some metals in combining with the particles of water, acids and oxygen make more energy efficient structures than others metals do. The iron displaced copper and magnesium displaced zinc in the above examples because in doing so they made for more energy efficient structures. They released photon energies in the process.
Try not to be confused by the term binding energy much used to explain the stability of a structure. The word binding makes it sound like it is an energy within the structure but that is just not so. The binding energy is the external energy we have to input to break its bonds. More stable, more energy efficient structures need greater inputs of binding energy to break their particle bonds. The reversal of many chemical reactions, like that when we charge a battery, requires input energies to break and rearrange particle bonds in a way that accommodates the increased energy.
In all chemical changes the least attached outer valence electrons play a major role. That is because they are more sensitive to the energy desires of surround structure protons. If it is more energy efficient to do so they will transfer their allegiance in full or in part to surround structures and thereby form bonds with them. Of course any such changes also brings a rearrangement of associated electrons and nuclei.
The groups and periods of the periodic table of elements tell us much about the distribution of energy gathering electrons around the nucleus of each element. The table groups tell us how many electrons are in the outer valence shell. As the inert gases of group 8 are most energy stable we can conclude that outer shells of 8 electrons are desired.
The transition metals that occupy the large section in the middle all have, along with the alkali earth metals, two valence electrons in their outer shell. We should not be surprised that they have many things in common. One thing they have in common is they will readily combine with the atoms of non metals in group 6. It is a way of securing a more energy efficient particle structure arrangement with 8 outer electrons. Similarly the alkali metals of group 1 will willingly combine with the halogens of group 7 .
Chemistry is a science that is all about energy formations.