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Notes from "Elemental"

These are my notes from "Elemental: How the Periodic Table Can Now Explain (Nearly) Everything", by Tim James. This book offers an entertaining, fairly easy to understand, picture of some of the elements in our world and what they do. It's be no means a textbook, but a good summary of random important concepts in chemistry. I thoroughly enjoyed it.

Things catch alight because they come into contact with oxygen. The only reason that things aren't bursting into flames is that, while oxygen is highly reactive, it needs energy to get going. Oxygen has to be heated in order to combust.

Chapter 5

On Earth the most abundant elements are oxygen, silicon, aluminum, and iron.

Planets are made from elements that began life inside an ancient star, blown to pieces by a supernova.

Chapter 6

The food in our mouth is sensed by the tongue and the nose simultaneously. This combination of smell and taste is what gives each food a flavor, that is, with the exception of spicy foods.

Quantum mechanics is what gave the periodic table its final form.

Chapter 7

Quantum mechanics is not one idea, but a sophisticated collection of theories that explain the world at its smallest level.

The fact that different elements have different shapes explains why they have different chemical behaviors.

Solving the Schrödinger equation for a particular element explains why it can be different from the element next door.

Chapter 8

There are only two things an electron can really do. It can move outward away from the nucleus, or inward towards it. These two behaviors underpin almost every chemical reaction.

When an electron jumps from one orbital to another, it's called a quantum leap.

If an electron absorbs a beam of light, it gets bumped to an outer orbital. And if it emits a beam of light, it drops to an inner orbital.

An electron gaining energy means losing stability and vice versa. This trade-off between ability and stability is what determines whether a reaction will happen or not.

Different kinds of light will produce different kinds of effects on an atom. Infrared light, which is too low in energy to interact with the electrons in our eyes so we can't see it, will cause the orbitals themselves to stretch and twist, rather than shunting electrons between them. Microwaves do something similar, except they cause the atoms to spin, rather than twist and bend. If you beam atoms with infrared or microwaves the result is that the atoms start dancing around and bashing into each other, exchanging energy. These twists and spins is what we call heat.

Picture a coat hanging on a coat hook. The coat will sit there until the end of time, even though it would achieve greater stability by dropping to the floor. That won't happen because you have to put energy into the systems first. It's only when you lift the coat up a few centimeters, freeing it from the hook, that you give it the option of falling into the more stable configuration. Electrons are exactly the same. We need to excite them first and get them out of their orbitals before they can drop into new ones. A stable molecule like water can be thought of as having a coat hook several meters long. You'd have to get on a ladder and lift the coat all that distance to get it free. That's why water reacts with hardly anything. Nitroglycerine on the other hand is like a coat hook a few millimeters long positioned over a cliff. A tiny nudge is enough to get the electrons out of their orbitals, and the subsequent energy drop is enormous.

Chapter 9

The repulsive force between protons in a nucleus has an infinite range, but the glue force from the neutrons doesn't. This means that large atoms have unstable nuclei.

Americium emits alpha particles constantly, so if you put it in an open circuit the charged particles can fly across a gap to a receiver and complete the circuit without wires. When flecks of smoke or dust float into this gap, the alpha stream gets blocked and an alarm triggers. This is how your smoke detector works.

Chapter 10

The more protons in an atom, the more electrons will be pulled inward and the smaller the atom becomes. This means we see a decrease in atom size along each row of the periodic table. The atoms on the left are therefore big and diffuse with floppy orbitals. Their electrons are a long way from the nucleus with nothing much keeping them in place. This makes them ideal for sharing electrons with other atoms. When you get these atoms together, their orbitals start mixing, not just on a 1 to 1 basis but over the entire population. The atoms are so happy to share, that when you solve the Shröedinger equations to describe millions of metal atoms, the result is a kind of mega-orbital - a turbulent free for all which physicists call the electron sea. This network of overlapping orbitals means that electrons can freely slosh from one side of the structure to the other.

A substance with a conductance of over 1 million siemens per meter is classified as a conductor, while a substance below 0.01 is an insulator. There's a huge gap between 1,000,000 and 0.01, but very few substances fall in this region. The ones that do are deemed semiconductors.

The only time electricity becomes lethal is if it passes through your lungs, heart, or brain for a sustained period of time.

If a current is pushed through the heart for a long period of time, it squeezes tight and doesn't reopen, meaning it can't take in a fresh load of blood. That's why people can survive lighting strikes but not the electric chair. The electricity of lighting may pass through your heart, but it does so for a short time only and your heart is able to return to normal.

Chapter 11

Liquid helium is the most fluid substance in the universe. If you take a cup of liquid helium and stir it, it will keep spinning forever. It has superfluidity.

The most common crystals on earth are based on silicon and oxygen, in the form of SiO2. It's the other elements mixed with them that give rise to the other elements we find in the ground. A single hunk of rock, a conglomerate of different mineral crystals mixed together, can contain dozens of elements. We have to extract them with acids or electricity.

Chapter 12

The food we eat contains sugars, which the body breaks down into the smallest type, glucose - C6H12O6. The glucose molecules then enter a sequence of reactions that convert them into water and carbon dioxide. The water is lost through sweat and the carbon dioxide dissolves into your blood, where it is carried to your lungs and breathed out.

With the exception of one species, every creature on Earth carries out Krebbs' reaction. It's called respiration, and it's the same thing, chemically speaking, as fire. Some chemical reacts with oxygen, producing carbon dioxide, water, heat, and light in the process.

Chapter 13

The rise of cancer really comes down to two numbers. Humans die. The older you get, the less you tend to function and the more likely you are to die from something like cancer or heart disease. The only reason we're seeing an apparent rise in these deaths is that people are lasting long enough to die from them. Age-related illness has been around since the rise of the human body, it's just that most people tended to extinguish before they got that far. The only reason that people live longer today is because we have defeated the world's number 1 killers. We don't die of infection anymore.

Most nuclear weapons today are based on plutonium, but uranium is still the starting ingredient.

A transistor's job is to let electrical current pass through it sometimes and block it at other times. Get enough transistors hooked up in an intricate pattern, and you've got a microchip. By programming a series of instructions for these transistors as 1s and 0s, we can tell transistors to switch currents on and off, allowing us to control circuits and store information. The problem with making a transistor out of metal is that metals always conduct. Similarly, insulators always insulate. To create something capable of switching on and off at different times, you need an element that is halfway between a metal and non-metal. Enter silicon.

Chapter 15

During the 1960s theoretical physicists decided it was time to take a bottom-up rather than a top-down approach. Starting with the basic laws of nature, what fundamental particles should we see arising? The resulting framework, called quantum field theory, predicts a buffet of particles, all of which have been found, so the approach is definitely along the right track.

Chapter 16

Shröedinger's equation is a full description of everything we can know about what a particle is doing. There are many different forms of the Shröedinger equation. The most common one is called the generalized time dependent Shröedinger equation.

The Shröedinger equation is telling us that if we can work out the total energy a particle has in a particular state, we can work out how its behavior will change with time. If you know what energy an electron has, you can predict where it's likely to be at any moment.


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