Electricity is produced through the movement of electrons between atoms. Normally, electrons orbit the nucleus of an atom but can be removed by adding energy. Some atoms have outer electrons that are farther from the nucleus and more easily removed. Copper and silver are good electrical conductors because their outer electrons are farther from the nucleus and repelled by multiple electron layers, making them easier to remove with just a small amount of energy. While silver is a slightly better conductor, copper is more commonly used due to its lower cost and greater abundance.

1. Electricity is Atomic !
Electrons from atoms make electricity.

2. Electricity is Atomic !
• Normally, an electron stays near or “orbits”
the nucleus of an atom.
• Electrons want to be as close to the nucleus
as possible. Why?
• Rule of our universe: Opposite electric
charges attract. Protons in nucleus are
positive and electrons are negative.
• Why don’t electrons combine with protons?

3. Electricity is Atomic !
• Electrons are not really particles.
• Electrons are somewhat like waves.
– Electrons can only exist at certain distances away
from an atom’s nucleus (or waves disappear).
• Electrons repel each other.
• Electron locations depend on positive “pull”
from protons in nucleus and negative “push”
from other electrons.

4. Electricity is Atomic !
• Adding energy to an electron doesn’t make it
move faster.
• Adding energy to an electron makes it move
farther away from the nucleus.
• If enough energy is added, an electron can be
removed from an atom completely.

5. Making electricity
• It takes added energy to make electrons
leave an atom.
• Some atoms have electrons that are more
easily removed.

6. Electrons come in
layers
• 1st layer can hold up to 2
• 2nd layer can hold up to 8
• 3rd layer can hold up to 18
• 4th layer can hold up to 18
• 5th layer can hold up to 32
• What is the most common conductor of
electricity?

7. Copper Atom
• 29 protons, 35
neutrons, and 29
electrons in 4 layers
• One single electron in
the outer layer, far
away from attracting
protons
• Give it a little energy
and it will jump off the
atom !

8. Electrons come in
layers
• A single outer (valence) electron is more easily
removed from an atom
• The further away from the nucleus, the less
the electron is attracted to the nucleus.
• The more layers of electrons repelling it, the
more easily the electron can be removed from
an atom.
• What is better than copper?

9. Silver Atom
• Single outer layer
electron
• Far away from
attracting protons in
nucleus
• Repelled by 4 layers
of electrons
• Outer electron very
easily removed

10. Gold Atom
• Single outer
electron.
• Very far from nucleus
• Repelled by 5 layers,
78 total electrons
• Silver is the best
electrical conductor,
not gold. Why?

11. Conductivity
• Conductivity = measure of a material’s ability
to conduct electricity.
• Silver = 63.0 M Siemens/m = 100 %
• Copper = 59.6 M Siemens/m = 94.6 %
• Gold = 45.2 M Siemens/m = 71.8 %

12. Why is silver a better conductor
than gold ?
• There is no simple answer to this question.
The mobility of electrons in any material
depends on lots of things other than the single
valence electron. It depends on the atomic
structure of the particular atom (what orbital is
the valence electron in, how strongly bound is
it, etc.) and also on the crystal structure of the
bulk material, the arrangement of nearby
atoms. Temperature also has an effect.

13. Why copper instead of silver ?
• Copper is less expensive
– $3.50/ lb vs. ~$300 / lb
• Copper is more abundant
– 15 million tons/yr vs. ~18 thousand tons/yr
• Nearly as good a conductor (94.6% as good)
• Better conductor than gold (24.2 % better)
– Gold plated on some electrical contacts because
it doesn’t corrode
• Copper is ductile and malleable