Monday, April 12, 2021

Nuclear Chemistry Definitions

General Chemistry Index

Where are we going with this? This page will assist in developing the ability to compare and contrast nuclear reactions with chemical reactions and to describe nuclear changes in matter, including fission, fusion, transmutations, and decays.

Nuclear Chemistry Definitions

So, if nuclear chemistry is the study of chemical reactions dealing with changes and transformations in the nuclei of atoms, we need to get some basic definitions down so we are sure what we are talking about!

Let's start with the very basics.

Atom: the most basic particle of matter made of protons, neutrons, and electrons.

Neutron: neutrally charged particles that make up atoms and which are found in the nucleus of the atom. Has a mass of about 1.

Proton: positively charged particles that make up atoms and which are found in the nucleus of the atom. Has a mass of about 1.

Electron: negatively charged particles that make up atoms and which are found in orbital (having fixed, specific energy levels) outside the nucleus of the atom. Has a very, very small mass compared to neutrons and protons.

Element: a specific type of matter defined by how many protons are present in the nucleus of its atom. Each element has a different atomic number.

Atomic number: the number of protons present in the nucleus of an atom.

Changing the number of protons changes the atomic number and, therefore, changes the name of the element!

Atomic Mass/Weight: The sum of the masses of all the parts of an atom (essentially, the protons and neutrons, since electrons have so little mass).


What happens if you change the number of neutrons in an atom?

Changing the number of neutrons changes the atomic mass of the atom. But, if the number of protons stays the same, it is the same element (by definition).

Isotope: A form of an atom having a non-typical mass because of the presence or absence of some number of neutrons.

Suppose you jam a neutron into hydrogen. The number of protons is still 1, but the mass is now 2. This is an isotope of hydrogen called deuterium. 


What happens if the number of protons and electrons are not the same?

Yeah, that can happen. 

It's fair to consider that an ion. 

Ion: a molecule/atom having a net positive or negative charge due to having too many or too few electrons (as compared to the number of protons).


So, armed with the above vocabulary, we can go on with all this nuclear chemistry stuff! But… since all the numbers seem to be subject to changing, we probably need some way of keeping up! Some system of notation for nuclear chemistry!


A few more things we need to know…

Alpha Particle

Some nuclear reactions involve injecting or emitting an alpha particle which is 2 protons and 2 neutrons (which gives it a charge of -2, but charge is not usually considered as part of nuclear reactions).

This is identical to a He nucleus. It's a helium atom without any electrons!

Beta Particle:

Some reactions involve taking in or ejecting electrons. 
ß- particle: a high-energy electron (negatively charged) emitted from a nuclear reaction.

Plot Twist! If you eject a ß- particle from a neutron, you get a proton!

Woo… didn't see that coming, did you? 


There is also a thing called a positron. Hang on to your hat!

Positron: essentially a positively charged electron. (Though that's really simplifying things!)

If a positron is emitted or recieved, it is also a beta particle. 

ß+ particle: a high-energy positron (positively charged) emitted from a nuclear reaction.

So back to the definition of a beta particle.

A beta particle is a high-energy electron (ß-) or positron (ß+), generally seen during emissions from the atomic nucleus during radioactive decay.


Naturally, agreement to the definitions is not universal. Some sources will zealously differentiate between the ß- beta particle and the ß+ positron. I actually prefer this as a way of avoiding confusion!  Some will describe "beta decay," the  ßemission, and "positron emission," the emitting of the ß+ , as distinctly different things.

Electromagnetic Radiation

Two other things closely related to nuclear reactions can be categorized as electromagnetic radiation. We should talk about that!

Most people interact with electromagnetic radiation… a lot. Constantly. In the form of…

Cell phone transmission
Microwave ovens
Radio (AM/FM/CB/Shortwave…)
and others…

Electromagnetic radiation is energy that radiates (or propagates) at the speed of light from a source.

Electromagnetic (EM) radiation is often modeled as a stream/wave of photons. Each type of EM radiation has a specific wavelength / frequency, but they all travel at c, the speed of light.

Photons are discrete energy packets (chunks) of electromagnetic energy which have properties of both particles and waves. Photons interact with matter in different ways, but frequently in a way that transfers energy from the photon to the matter. Different types of photons carry different amounts of energy.

Because photons can act as, at time, a particle, and, at other times, as a wave, they are sometimes thought of as wave-icles. Photons also are described as…

a beam of…
a ray of…
waves of…

Gamma Ray:

Many nuclear reactions emit electromagnetic energy from the nucleus in the form of gamma rays. A gamma ray is a penetrating form of EM radiation with extremely short wavelength and very high photon energy. 


Reactions involving electron capture will produce energy in the form of x-rays. X-rays are a high-energy form of EM radiation that penetrates and passes through most matter having short wavelengths and high photon energy.

How are x-rays, and gamma rays different, you ask? They have very similar properties, but gamma rays come from the nucleus of the atom and x-rays come from outside the nucleus. X-rays have lower energy than do gamma rays, as well.

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