Last updated 9-28-11
<-Building Blocks <-CHM130S <-CHM107

C2: Protons, Neutrons, and Electrons Built from Energy
To view his tutorial written in Romanian, click here

To illustrate how chemistry is all about building blocks, we will attempt to make a cake from scratch. Totally from scratch. The only starting ingredient we have is ENERGY!
Somehow we need energy to turn into particles. But is that even possible?

We do have convincing evidence of the reverse (mass turning into energy) according to Einstein's famous equation. Energy equals mass (m) times speed of light (c) squared.

In the atomic bomb, some of the mass of uranium gets converted to energy. Much of that energy is gamma rays, which are photons of high energy light.

The equation allows us to figure out how much energy is in mass. It could also be interpreted as how much energy is needed to create a certain amount of mass. Let's consider the mass of our cake to be 1 kilogram (about 2.2 pounds).
E=1 kilogram x (300,000,000 meters per second) x (300,000,000 meters per second)
Energy is the mass (in kilograms) times speed of light (in meters per second) squared.

E= 90,000,000,000,000,000 joules.

The amount of energy will be measured in "joules." A joule is the energy used by one watt going for 1 second. The penlight is about 1 watt. So turn it on for one second and you consume one joule of energy. So one joule isn't much, but 90,000,000,000,000,000 (90 quadrillion) joules is.

We don't normally buy electricity measured with watts times seconds, we buy kilowatts (1000 watts) times hours. Notice the arrow points to kilowatt hours. We pay about 11 cents per kilowatt hour. A toaster consumes about 1,000 watts, so it costs 11 cents to run a toaster for an hour.

90,000,000,000,000,000 watt seconds x kilo x  1 hour   
1000    3600 sec.

25,000,000,000 kilowatt hours
or 25 billion kilowatt hours

We've replaced joules with watt seconds (which means watts x seconds). By dividing by 1000 and 3600, we get kilowatt-hours.

This is the Palo Verde nuclear power plant. It can generate about 4,000,000 kilowatts of power. (Same as powering 4 million toasters). Divide 4,000,000 kilowatts into the 25,000,000,000 kilowatt-hours needed, gives us hours. The answer is 6,250 hours or 260 days. So Palo Verde nuclear power plant would have to put out maximum power 24 hrs a day for 260 days to create enough energy to create the 2.2 lbs of matter for our cake. Our electric bill will be 3 billion dollars. I didn't say making a cake from scratch was cheap.
What we need is 3 billion dollars worth of high energy photons called gamma rays. A photon is a packet of light. It travels in waves. The higher the energy the closer the waves are. Unfortunately, electric companies produce electricity not photons.
In some parts of the universe, gamma rays are plentiful.  Below, a black hole (a collapsed star) is devouring another star.  As the material falls into the black hole, jets of particles and gamma rays shoot out.  These gamma rays could produce the matter we need. But going there is impractical.
Also, when the universe was young, it was filled with gamma rays, so the creation of matter was common. But now, we have to work hard to create gamma rays here on Earth.
Fortunately, there are huge facilities (below) that can accelerate particles and smash them into targets and make gamma rays. The image in the upper right, shows the tracking of particles inside a cloud chamber. The yellow arrow shows were a high speed particle collided with another particle. Four particles scattered. Gamma rays were produced (but you can't see their trail). The green arrow shows were the gamma rays joined to form two new particles that split away from each other in a loop motion. The bottom loop is an electron and the top loop is a positron (an anti-electron). Electrons have a negative one charge and positrons have a positive one charge. They loop in opposite directions because there is a magnetic field in this chamber, which causes charged particles to move in curved paths. Also, opposite charges curve in opposite directions.
One way we create light is to accelerate electrons and then slam them into a metal plate. We accelerate them by crowding them on a wire. They will repel each other, and in doing so an electron might break away from the wire. Also, if you have a metal plate with an excess of positive charge, the electron will accelerate towards that plate. Electrons slam into the plate and come to stop. That energy of moving fast has to go somewhere (kinetic energy is energy gotten from motion). That energy normally is converted to light. With 2 or 3 volts, the light is visible light you can see. With 110 volts (like an arc welder) you also get ultraviolet light, which you can't see. But ultraviolet light has enough energy to damage your eyes. At 100,000 volts the light given off is x-rays. X-rays have the energy to pass through objects, but not enough energy to convert to particles. However, at 1 million volts...
A million volts is enough to push a spark several feet. The guy belows likes to build Tesla coils. This one is producing about half a million volts. The sparks below are slowed down by air. But if he could double the voltage and have the electrons in the sparks fly through a vacuum and slam into a metal target, the resulting light created would be gamma rays.
With a million volts, the light created when the electrons come to halt will be gamma rays. When two of these gamma rays collide, they can disappear and in their place will be two new particles. In this case one electron and one positron. For our cake, we only want the electron. Of course, we will need a lot of electrons.
To make a cake, we need the elements carbon, hydrogen, oxygen, nitrogen, and sulfur. However, electrons aren't enough to build these elements, we need protons and neutrons. If we crank up the voltage to one billion volts, our higher energy gamma rays could produce protons and neutrons. Anti-protons and anti-neutrons (antimatter) are also produced, but we only want the protons and neutrons. A billion volts is enough to create a lightning bolt that reaches halfway around the Earth.
After spending 3 billion dollars for 25 billion kilowatts-hours of energy, and creating voltages that could send lightning bolts around the world, we end up with enough neutrons, protons, and electrons to make our cake. These three particles are the first solid building blocks. Light was the first building material, but it's hard to call light blocks.
In the next tutorial, we learn how these three particles become building blocks for all the elements.
<-Building Blocks <-CHM130S <-CHM107

Since Sept 19, 2004