Electrons are massless ?

  • Thread starter Cosmo16
  • Start date
138
0
Electrons are "massless"?

Why are electrons described as "massless". It seems to me that they would have to have mass. Are they truly massless or is this the same kind of aproximation that is made with ideal gas laws?
 

Astronuc

Staff Emeritus
Science Advisor
18,547
1,682
http://hyperphysics.phy-astr.gsu.edu/hbase/particles/lepton.html#c2

An electron is a lepton with rest mass of 0.511 MeV (or 9.11 x 10-31 kg).

Compared to a proton of rest mass 938.27 MeV (1.6726231 x 10-27 kg), the electron is light, but not massless.

Perhaps the article cited by ZapperZ indicates that electrons in certain conditions behaves as massless particles.

From the article on PhysicsWeb -
Two teams of physicists have discovered previously unseen exotic behaviour in sheets of carbon atoms. The teams have shown that electrons move through the sheets as if they have no rest mass. They have also observed a minimum value of conductivity for the sheets and an unusual form of the quantum Hall effect (Nature 438 197 and 201).
Further investigation has revealed
that the electrons in graphene behave like relativistic particles that have no rest mass and travel at about 106 metres per second. Although this is a factor of 300 slower than the speed of light in vacuum, it is still much faster than the speed of electrons in an ordinary conductor. Moreover, the electrons in most conductors can be described by non-relativistic quantum mechanics, whereas the electrons in graphene need to be treated as relativistic particles called massless Dirac fermions.
Go to Zz's thread https://www.physicsforums.com/showthread.php?t=99223
 
Last edited:
138
0
well, my chem teacher calls them masssless, which annoys me, which is why asked.
 

Pengwuino

Gold Member
4,854
14
Cosmo16 said:
well, my chem teacher calls them masssless, which annoys me, which is why asked.
Chemistry people are nuts :P

Is this high school? College professors wouldn't make such a mistake....
 
138
0
ya its HS. Cool guy, really good teacher , I think he just doesn't want to confuse the rest of the class when were doing atomic mass. At least, I'm assuming that what is was.
 

Pengwuino

Gold Member
4,854
14
Yah that is probably the reason. When i was in high school, i was like "wait wait wait, you didn't add in the electrons :(". He still shouldn't say they are massless however, he should just say they are too small to be considered in weighing masses at a high school level.
 
138
0
he might have said they were negligible once.
While i'm on the topic- gamma rays (edit:particles not rays) have mass- correct?
Cause he did say that those were massless.
 

Pengwuino

Gold Member
4,854
14
There is no such thing as a gamma particle. Gamma rays are massless however.
 
138
0
ok, maybe it is gamma rays I am thinking of then, we were doing radiation, he was talking about it like it was a particle, but then he called it a ray, left me kinda confused.
 

Pengwuino

Gold Member
4,854
14
Well it's an electromagnetic wave as far as i know :)
 
78
0
about gamma-rays... They shouldn't be the electromagnetic waves with the most corpuscular behaviour? The great deal of particle aspect of light (i.e. see Compton effect: a photon come to act like a ball that on a pool table matches another one, the electron, which is a really material particle despite gamma-ray!) is to attribute to them!
It is a strange dualism, for which some people have never come out!


Sorry for my spit-joint english

airman:shy:
 

Mk

1,963
3
Cosmo16 said:
ok, maybe it is gamma rays I am thinking of then, we were doing radiation, he was talking about it like it was a particle, but then he called it a ray, left me kinda confused.
Well, there's alpha particles, beta particles, and gamma particles/rays. Gamma rays, are photons, electromagnetic radiation. Wave-particle duality. And photons kind of have mass and kind of don't... rest mass they do have.
 

ZapperZ

Staff Emeritus
Science Advisor
Education Advisor
Insights Author
2018 Award
35,127
3,927
Mk said:
Well, there's alpha particles, beta particles, and gamma particles/rays. Gamma rays, are photons, electromagnetic radiation. Wave-particle duality. And photons kind of have mass and kind of don't... rest mass they do have.
Whoa! Since when?

Zz.
 

Related Threads for: Electrons are massless ?

  • Posted
Replies
13
Views
6K
Replies
4
Views
2K
Replies
6
Views
4K
  • Posted
Replies
5
Views
7K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top