Electrons

Scanning electron microscopy (SEM) is a powerful imaging technique which produces a largely magnified image by using electrons and X-rays instead of light. Primary electrons come from the electron gun situated at the top of the microscope. Secondary electrons originate from the specimen as a result of displacement by the primary electrons. Backscattered electrons consist of high-energy electrons originating in the primary electron beam that are reflected or back-scattered out of the specimen. SEM can be coupled with an X-ray spectrometer which is called energy-dispersive X-ray spectroscopy (EDX). At rest, an atom within the specimen contains ground state electrons. The primary electrons from the electron gun excites an electron in an inner shell, prompting its ejection as a secondary electron, resulting in the formation of an electron hole within the atom’s electronic structure. An electron from an outer higher energy shell then fills the lower energy hole, and the excess energy is released in the form of an X-ray photon. Each element of the periodic table emits X-rays at distinctive energies due to distinct elemental electronic structure. Thus, X-ray emission data can be analysed to characterise the elemental composition of the specimen and also perform area mapping.

Craig Beals explains the structure of the atom: Protons, Neutrons, Electrons. And the concepts of Ions, Isotopes and Radiation. Periodic Table: https://commons.wikimedia.org/wiki/File:Periodic_table_large.png Isotopes of Carbon: https://en.wikipedia.org/wiki/Isotopes_of_carbon

We'll learn about oxidizing agents and reducing agents, what they are, what they do, and how to identify them in chemical equations. Oxidizing agents make oxidation happen, and reducing agents make oxidation happen. And oxidizing agent takes electrons from something, allowing it to be oxidized, and a reducing agents gives electrons to something, allowing it to be reduced. You can remember this by noting that the thing that is reduced is the oxidizing agent, and the thing that is oxidized is the reducing agent. We'll then look at some equations and identify the oxidizing and reducing agents. To do this, we have to write oxidation numbers (or oxidation states) for the elements in the equation, and then figure out how electrons are moving, what is being oxidized and what is being reduced.

This is an introduction to oxidation reduction reactions, which are often called redox reactions for short. An oxidation reduction (redox) reaction happens when electrons are transferred between atoms. A loss of electrons is called oxidation, and we say that atom has become oxidized. A gain of electrons is called reduction, and we say that the atoms has become reduced. The two separate parts (oxidation and reduction) of an oxidation reduction (redox) reaction are called half reactions. Two half reactions can be put together to make the whole reaction. Oxidation numbers are numbers that can be written above atoms to show whether they are gaining or losing electrons.

We'll go step by step through how to balance an oxidation reduction (redox) reaction in acidic solution. Most importantly, both charges and atoms must balance. Here are the steps: first, calculate oxidations numbers for all the elements in the equation. Next, figure out what is being oxidized and what is being reduced. Then, write half reactions for the oxidation and reduction. After that, balance each half reaction: first, for the atoms other than O and H, then for O and H, and finally for charge by adding electrons. After being balanced, the oxidation and reduction half reactions are ready to be added back to together. Make sure that the number of electrons is the same in the oxidation and reduction half reactions. If they are not, multiply one or both of the half reactions to make the number of electrons the same. Then, combine the oxidation and reduction half reaction, canceling out stuff that appears on both sides of the equation. Lastly, do a final check to make sure that everything balances: both atoms and charge.