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Introducing Our Acquaintance, the Atom:
Reposted from my blog, Doomsday Writer originally posted January 15, 2020
Since nuclear weapons unleash the power of the atom in explosions of amazing destructive power, it’s necessary to understand what an atom is to better be able to understand what they can do.
Atoms are the smallest particles of matter that make up chemical element – which are things like oxygen, carbon, helium, iron, silver, gold and (for our purposes) uranium and plutonium. Atoms are incredibly small (and are actually made up of smaller bits, which are themselves made up of even smaller bits).
One atom is one ten-millionth of a millimeter or 1/254,000,000 of an inch. Trying to get your head around the atomic scale is pretty much the reverse of trying to grasp the cosmic scale, but Corridor Crew’s video “VFX Artist Reveals the True Scale of Atoms” is helpful for getting the idea across.
Atomic Structure: Atoms are composed of two main components: the electron and the nucleus.
- Electrons – negatively particles that orbit around the atom’s nucleus. Traditionally, at least since 1913, this has been depicted as being similar to the way planets orbit the Sun: in neat, circular orbital paths that never cross over with each other. This model is inaccurate, at least for elements other than hydrogen, but it suffices for our purposes.
- Nucleus – the core of the atom which is made up of:
- Protons: positively-charged particles that make up the bulk of an atom’s mass. They’re positively-charged particles; they are the bulk of an atom’s mass, being about 2000 times heavier than the electron. The number of protons in a nucleus is always the same and is equal to the element’s atomic number.
- Neutrons: have no charge and are, therefore, neutral particles. They are slightly heavier than protons. The number of neutrons in a nucleus can vary from atom to atom, even within the same element. These variations are called isotopes (more on this in a minute)
It’s Particles All The Way Down:
Electrons are considered to be elementary particles, since they cannot/do not break down any further. Protons and neutrons on the other hand can be broken down into smaller elementary particles called quarks, which are held together with gluons (because they “glue” the quarks together into larger particles).
There’s a whole zoo of elementary particles, most of which are not germane to our discussion. Suffice it to say that Augustus De Morgan’s 1872 poem, "Siphonaptera"is a fairly apt description of an atom (just substitute "particles" for "fleas"):
Great fleas have little fleas upon their backs to bite 'em,
And little fleas have lesser fleas, and so ad infinitum.
And the great fleas themselves, in turn, have greater fleas to go on;
While these again have greater still, and greater still, and so on.
Elements and Isotopes:
Elements are substances that contain only one type of atom and cannot be broken down into a simpler substance. There are 92 naturally occurring elements and 24 synthetic elements (i.e. elements first created in laboratories, though some of these have since been found in nature). They are the building blocks of other matter.. [(1)]
All atoms of a particular element have the exact same number of protons. The number of protons in a nucleus is element’s atomic number. Hydrogen’s atomic number is 1; uranium’s atomic number is 92. All hydrogen atoms will have 1 proton; all uranium atoms will have 92 protons. On the periodic table, elements are ordered, in part, by their atomic numbers.
The total number of protons and neutrons in an atom is known as the atom’s mass number. While the total number of protons in an atom’s nucleus will always remain the same, the total number of neutrons can vary from atom to atom. [(2)]
This variation is called an isotope and is usually written as the element’s name (or abbreviation) along with the isotope’s mass number. [(3)]
For example: the most common isotope of carbon has a nucleus that holds six protons and six neutrons. It’s written as carbon-12 or C-12.
Isotopes can be heavier or lighter than the standard for their element. For our purposes, think of isotopes as variant cover versions of a comic book. The difference in the number of neutrons won’t alter an element’s chemical properties, any more than an alternate cover will change the story inside the comic book.
What the difference in neutrons does affect is how stable and, therefore, how radioactive an isotope is.
Elements and stability: Elements can be stable or unstable, depending on how well they hold onto their neutrons and protons. Think of a shopper trying to fill a bag with apples and oranges. For our purposes, the shopper is the atom, the fruits are the protons (apples) and neutrons (oranges) that make up the nucleus and the bag is the binding force that holds the nucleus together.
In the case of a stable atom/element, the bag is strong enough to contain the fruit without tearing. With an unstable atom/element, the bag isn’t strong enough so it tears and allows an apple or orange to spill out and go bouncing off to cause citrusy chaos.
- Stable atoms/elements are not radioactive and do not emit radiation. Carbon-12 is an example of a stable element.
- Unstable atoms/elements are radioactive and emit radiation through radioactive decay (more on this in a moment). Carbon-14 is an unstable element, which is a big part of why it is used to help date certain archaeological finds.
Radioactivity, Radiation and Radioactive Decay:
Radioactivity is, according to Merriam-Webster.com, “the property possessed by some elements […] of spontaneously emitting energetic particles […] by the disintegration of their atomic nuclei.”
Radiation is, also per Merriam-Webster.com, “the process of emitting radiant energy in the form of waves and particles [and/or] the combined processes of emission, transmission, and absorption of radiant energy”. Scientifically speaking there are several different types of radiation, but the ones we’re most concerned with are:
- Electromagnetic radiation: which includes radio waves, microwaves, infrared, the visible light spectrum, ultraviolet, x-rays and gamma radiation.
- Particle radiation: which includes fast-moving subatomic particles such as alpha particles, beta particles and neutrons.
Radiation can be further categorized as being ionizing or non-ionizing radiation. Both types can come in the form of particles or waves. The differences are:
- Ionizing radiation is high-energy radiation that can directly disrupt chemical bonds by stripping electrons from atoms. In living tissue, ionizing radiation can cause damage to proteins, to DNA and damage or destroy cells.
- Types of ionizing radiation: X-rays, gamma rays, ultraviolet B (UVB) and ultraviolet C (UVC ) rays, alpha and beta particles, neutrons.
- Non-ionizing radiation: is lower energy radiation that cannot disrupt chemical bonds, but instead can increase the thermal energy of atoms and molecules (aka heat)
- Types of non-ionizing radiation: radio waves, microwaves, infrared and visible light, and ultraviolet A (UVA) radiation.
Radioactive Decay: Stable elements, like Popeye, are what they are and that’s all that they are. They do not change, even during a chemical reaction they stay who they are. Coal is, primarily, made of carbon. When you burn coal, its carbon atoms don’t change into another kind of atom.
Unstable elements change over time. This process of change was first discovered by French physicist Henri Becquerel in 1896; it was confirmed – and named radioactive decay – by Marie and Pierre Curie in 1898. Both Becquerel and the Curies were awarded the Nobel Prize in Physics for this discovery in 1903
Nutshell Definition: radioactive decay occurs when an atom undergoes a random change that causes it to turn into something else – either a different isotope of itself (C-12 becoming C-14) or into an entirely different element, which can be stable (Uranium-238 to Lead-206) or unstable (Uranium-238 to Thorium-234). This process is called a decay chain.
There are, of course, different types of radioactive decay. We’re going to be focusing on the three that seem to come up the most with regards to nuclear weapons:
- Alpha decay – the nucleus of the atom emits an alpha particle (two protons and two neutrons; essentially a helium-4 nucleus). Alpha particles are, generally speaking, mostly harmless to humans and can be shielded against by a piece of paper. [(4)]
- Beta decay – the nucleus of the atom emits a beta particle, either by releasing a negatively-charged electron, causing a neutron to change into a proton (beta-minus decay) or releasing a positron (essentially a positively-charged electron) and a proton becomes a neutron (beta-plus decay). Beta particles are able to penetrate living tissue, but can be shielded against by, among other things, a few millimeters of aluminum. [(5)]
- Gamma decay – After a nucleus emits either an alpha or beta particle, the new “daughter nucleus” is usually left in a high-energy, excited state. If so, it may decay by releasing a gamma ray photon. Gamma radiation has little trouble passing through substances, especially the unshielded human body, which makes it the most immediately dangerous. Shielding against it requires thick, dense materials, like lead. [(6)]
Next time, we'll take a look at the health effects and risks associated with exposure to radiation.
Footnotes:
- [1]Note on Compounds and Molecules: Compounds are combinations of two or more different elements; water is a compound formed from one oxygen atom and two hydrogen atoms; table salt is a compound of chlorine and salt.
Molecules are groups of atoms; they can be a collection of atoms of the same element (an iron molecule) or a collection of compounds (a water molecule) - [2]Hydrogen Isotopes are a bit different than other elements’ isotopes. It’s most commonly found isotope, hydrogen-1, doesn’t have a neutron. Other hydrogen isotopes, starting with hydrogen-2 and higher, do have neutrons. Hydrogen isotopes also have proper names in their own right: hydrogen-1 is known as protium; hydrogen-2 is deuterium and hydrogen-3 is tritium. To further add to confusion? Deuterium has one proton and one neutron; tritium, 1 proton and 2 neutrons; hydrogen-4, 1 proton and 3 neutrons and so on and so forth.
- [3]Or as 12C or 12C, which seems to be more in use by actual scientists. Since I’m not an actual scientist, I’m going to stick with the element-number versions because those are easier to write and (for me) to code into html.
- [4]So long as they stay outside the human body, alpha particles are entirely harmless. If they get inside the human body, by being inhaled, consumed with food/drink, or enter through broken skin, they can cause significant amounts of internal, long-term damage, mostly by increasing cancer risks.
- [5]Beta particles are more dangerous than alpha particles, since they can penetrate unshielded skin. Like alpha particles, the main risk is an increased, long-term cancer risk.
- [6]If you don’t have any lead handy, you can also shield yourself from gamma rays using other materials – but you’re going to need to use more of them. For example, you can get the same protection as 1.3 feet of lead by using 13.8 feet of water or 6.6. feet of concrete. (source: http://nuclearconnect.org/know-nuclear/science/protecting)
Note on Sources and a Caveat/Plea for Mercy:
In addition to the sources cited directly in this article, I also made use of information from Wikipedia, both the standard English version and the Simple English version
I also made use of information from Using Medicine in Science Fiction: The SF Writer’s Guide to Human Biology by H. G. Stratman, specifically from chapter 6, Danger! Radiation!.
Any errors in this article are my responsibility. In my defense, I am not a physicist and my last chemistry class was during the Reagan administration. If you find an error, please bring them to my attention and I will correct them.
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Originally posted at: Nuke Opera 2020: Introducing Our Acquaintance, the Atom January 15, 2020
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