76 lines
3.1 KiB
Markdown
76 lines
3.1 KiB
Markdown
---
|
|
tags: [physics, electricity]
|
|
---
|
|
|
|
# Electrons
|
|
|
|
## Shells
|
|
|
|
Electrons orbit in concentric circuits around the nucleus of the atom. Each
|
|
orbit is called a **shell**.
|
|
|
|
Each shell can accommodate a maximum number of electrons. The shells are
|
|
designated by letters and filled in sequence moving out from the shell nearest
|
|
to the nucleus.
|
|
|
|
_The diagram below demonstrates shell naming conventions and the maximum number
|
|
of electrons per shell._
|
|
|
|
|
|
|
|
## Valence
|
|
|
|
The outer shell called the **valence shell** and the number of electrons it
|
|
contains, the **valence**. This part of the atom is the most important from the
|
|
point of view of electricity because it is from here that electrons can escape
|
|
the atom and where electrons from other atoms may join.
|
|
|
|
> The farther the valence shell is from the nucleus, the less attraction the
|
|
> nucleus has on each valence electron. Thus the potential for the atom to gain
|
|
> or lose elections increases if the valence shell is not full and is located
|
|
> far enough away from the nucleus.
|
|
|
|
## Conductivity and insularity
|
|
|
|
The **conductivity** of a material is an expression of its capacity to channel
|
|
electrical charge. Where electrical charge is the _flow of free electrons from
|
|
one atom to another_. The **insularity** of a material is the opposite: its
|
|
_capacity to resist the flow of electrical charge_.
|
|
|
|
Electrons in the valence shell can gain energy from external forces. If these
|
|
electrons gain enough energy, they can leave the atom and become **free
|
|
electrons**, moving randomly from atom to atom.
|
|
|
|
We call materials that contain a large number of free electrons **conductors**.
|
|
In contrast **insulators** are atoms that stabilize themselves by absorbing
|
|
valence electrons from other atoms to fill their valence shells, eliminating the
|
|
free electrons.
|
|
|
|
> The propensity for the electrons within a conductor to move about and jump
|
|
> between atoms, swapping charge, is not something that is only activated when a
|
|
> voltage is applied. In fact, the electrons are always doing this, even in a
|
|
> piece of inert copper. The difference is they are doing it randomly and in all
|
|
> kinds of directions. It is only when a voltage is applied that the motion and
|
|
> exchange of electrons is forced in one consistent direction.
|
|
|
|
### Semiconductors
|
|
|
|
Semiconductive materials are midway between conductors and insulators: they are
|
|
neither good conductors or insulators but can be altered to function in the
|
|
manner of either.
|
|
|
|
## Ionization
|
|
|
|
Ionization is the process of atoms gaining and losing electrons.
|
|
|
|
When an atom has an equal number of protons and electrons it is said to be
|
|
**electrically balanced**.
|
|
|
|
A balanced atom that receives one or more extra electrons gives way to an
|
|
overall negative charge. An atom in this state is a **negative ion**. Conversely
|
|
if a balanced atom loses one or more electrons it becomes positively charged and
|
|
is thus called a **positive ion**.
|
|
|
|
> The process of ionization is a constitutive part of the flow of current but
|
|
> not the only part. We also must factor the force that triggers ionization and
|
|
> the resistance that impedes it.
|