Electronics 101: Atomic Structure

An explanation of the way Atoms work in from an Electronics points of view.

Guide

The Atom

All matter is made out of 'atoms'. The word 'atom' was originally intended to imply that which is the smallest possible building block that the world consists out of. We have since discovered that there are many more smaller particles than what we call the "atom", which the atom itself consists out of. From an electronics engineering perspective, there are only three properties of the atom that we are interested in: 

1.  The Proton
2.  The Neutron
3.  The Electron

Today when we refer to an "atom" we specifically refering to the smallest particle of an element that retains the characteristics of the element.  
There are at least 109 confirmed atoms; each having different charactersitics than another. Therefore, each element has a unique atom structure.

The standard model of representing Atoms is according to the "Bohr model" with each atoms acting as planetary type of structure, surrounded by orbiting Electrons while the Protons and Neutrons are located & concentrated in the center. The combination of the Protons and Neutrons are called the Nucleus of the Atom.
The simplest atom is that of Hydrogen which has only one proton and one electron.
Helium has two protons, two netrons and two electrons orbiting the nucleus.
If there are more protons in the atom than there are electrons then the atom is Negatively Charged and thus the atom itself has the capability to bring itself to a state of equilibrium by obtaining electrons from neighbouring atoms.

Atomic Number

All elements in the periodic table are ordered according to their "Atomic Number". The Atomic Number refers to the number of protons in the nucleus of the atom.

Helium for example has an Atomic Number of 1 because there is 1 proton in the nucleaus. If the Atom is in a normal state and not negatively charged then there will be the same amount of electrons as there are protons as well.

Electron Shells and Orbits

According to the "Bohr model" of the Atom, Electrons orbit the nucleus of an atom at a certain distance from the nucleus. Much like planets orbiting the sun (in which case our whole solar system would represent a single atom, the nucleus being the sun and the electrons as the planets). 

Unlike planets however, electrons can only ever orbit at specific discrete distances from the nucleus. If an electron wants to change the distance that it orbits from the nucleus then the electron needs to 'jump' to the next field of orbit. In our planetary example where electrons are represented by planets in our solar system then this would mean that if some sort of force tried to move the Earth further away from the sun then the Earth can only either move into the orbit that Mars (our closest neighbour's orbit). According to the Bohr model of the electron there is a an energy force that exists between the diiferent orbit distances and therefore an electron can only ever be located at a specific oribit from the nucleus. 

Each discrete distance (orbit) of the elctron from the nucleus of the atom corresponds to a certain energy level. The orbit (distance from nucleus) along with the energy bands associated with that orbit of an Atom is collective known as an Electron Shell, often just refered to as "shells".  

Each Atom at has a specific number of electron shells. Each of shell in an atom has a fixed number electrons permissible/allowed per shell. The energy difference between any point within a shell is always less than the energy difference between different shells. Therefore, it is easier for an electron to move around within its current shell than it is for it to a higher or lower shell. Hence, electrons tend to stay within their orbits.

The shells in an Atom are designated as 1,2,3,4 and so on. The shell closest to the nucleus is shell 1. The number of shells within an Atom is determined by the Atomic Number (the periodic table). 

Valence Electrons

Electrons that orbit farther from the nucleus have higher energy and are less tightly bound to the atom than electron closer to the nucleus. 

The reason why electrons in have more energy the further away from the nucleus they orbit is because the force of attraction between the positibely charged nucleus and the negatively charged electron decreases as the further away an electron is from its nucleus. 

Electrons in the outer most shell of an Atom has the most energy but also is the most loosely bound to the atom. This rule therefore gives great importance to the outmost shell of an Atom and is called the Valene Shell and, any electrons within this shell are called Valence Electrons.

The concept of Valence Electrons is extremely important and is used in a variety of fields and operations, including those of chemical reactions, the bonding properties within the structure of a material and, its electrical properties. 

Ionization

When an atom absorbs energy from an external source such as from heat or from light then the energy levels of the electrons are raised. This means that the valence electrons posses more energy than normal but are still just as loosely bound to the atom and therfore require less energy for the valence electron to break free from the atom.

Electron per Shell

The maximum number of electrons that can exist in each shell of the atom is determined by nature and can be calculated with the formula:

Ne=2n²

Where 'Ne' represents the number of possible electrons in the shell and 'n' is the shell number.

Therefore the maximum number of electrons that can exist in the first four shells of of atom is:

Shell 1: 2 Electrons
Shell 2: 8 Electrons
Shell 3: 18 Electrons
Shell 4: 32 Electrons

Shell n: (2*n²) Electrons

All the shells in an atom must be completely filled with electrons except for the outermost shell, the Valence Shell.

Conclusion

This should provide you with all the information needed to to undestand the structure of an Atom as it relates to the field of electronics. If you feel more information is needed then contact Leobot at any time! We will gladly help you in any way we can.

Feel free to have a look at the next guide in this series.

 Next: ELECTRONICS 102: CONDUCTORS, INSULATORS AND SEMICONDUCTORS