# How can an atom give off energy and remain the same size?

Discussion in 'Physics & Math' started by Christmas 1996, Aug 26, 2004.

1. ### Christmas 1996Registered Senior Member

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It's said that energy moves in quanta.

We are also told that Protons, Electrons and Neutrons are the smallest things in existence, meaning that they can't lose weight, thus meaning that they're, presumably, the matter version of quanta, yeh? So how is it that energy can be given off them and thus, presumably, lose mass? I mean, a proton can't become smaller, but it must be if it's given off energy?

3. ### James RJust this guy, you know?Staff Member

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30,358
There are lots of different kinds of energy.

Take a single particle, like an electron. If it is just freely moving around by itself, it has a certain fixed amount of energy due to its mass, plus some kinetic energy which is due to its speed.

Now consider a hydrogen atom, for example. That consists of a single electron orbiting a proton. The atom as a whole has kinetic energy due to movement of the whole atom through space. Each particle in the atom has rest mass energy, and some kinetic energy as well. But now there is a new type of energy - electrical potential energy between the proton and the electron, which comes from the fact that opposite electric charges attract each other.

The electron in the hydrogen atom can have different values of its kinetic and electrical potential energy, depending, roughly, on its orbital speed and distance from the proton. It is possible for the electron to lose or gain energy, yet still remain in orbit.

5. ### wesmorrisNerd Overlord - we(s):1 of NValued Senior Member

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9,844
That's where "energy levels" come in. James could you give a brief description of how energy levels play into this? Aren't they discrete? I barely remember how it works from university physics.

Oh hey wait, this site seems to give a simple enough description: http://www.colorado.edu/physics/2000/quantumzone/bohr2.html

7. ### philocrazyBannedBanned

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234
you people are dumb im so sorry
saying that you have discovered the atom is like saying i am god
im sorry there's no basis for atom
but all you have discovered is chemical substances, matter that you can
identify
the universe is an atom so atom=atom what is atom=chemical thus
chemical < atom where atom + chemical =(chemistry)
power=stored energy>mass - matter where proof= nuclear explosion
but you dont know the atom that makes piss piss
and you are the animal who has discovered all this!!!!!!!!!!!!
take it to the next animal level make a rocket bomb!!!!!!!!!!!!
i am the atom
and you can never split me asshole (universe)

Philosopher Philocrazy

8. ### James RJust this guy, you know?Staff Member

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30,358
Making about as much sense as usual there, philocrazy.

9. ### Christmas 1996Registered Senior Member

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56
you're saying that the kinetic energy in an electron when it drops to a lower shell(?) is turned into a photon? but don't scientists usually say that energy is merely a liberated form of matter?! Doesn't that mean that protons\electrons\neutrons can be transformed into energy?

Last edited: Aug 27, 2004
10. ### NasorValued Senior Member

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6,221
Yes, you could transform the mass of a subatomic particle like an electron into light – but that’s not what usually happens when light is emitted from an atom. The energy from the light generally comes from a decrease in the potential or kinetic energy of the electron as it orbits the nucleus.

11. ### rumborakRegistered Member

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I think nonetheless the mass will decrease.
The only problem is that the amount of energy given off in photons is miniscule compared to the energy from E=mc^2, so the decrease of mass is probably not big enough to be measureable.

rumborak

12. ### blobranaRegistered Senior Member

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2,214
@rumborak
hum,
So eventually every electron in the universe will decrease to nothing...

Or are they topped up?

i imagine their masses set, er, due to being leptons/(quark) etc.
i think, they get their mass from interacting with a higgs field so that it's impossible to get a skinny or fat electron (er, at rest mass).

it's like a can of coke, you can pour out only a certain amount of juice but once its empty, its empty - you cant pour out the aluminium, because that<b>is</b> the can..

13. ### NasorValued Senior Member

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6,221
The electrons around an atom will only emit light if they're in an excited state. If they're in the ground state (lowest energy level) they just sit there.

14. ### cckieranHighSchool Phys/Chem studentRegistered Senior Member

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Protons and neutrons are made up of smaller particles called quarks. Neutrons can in fact become smaller, by decaying into protons, electrons and antineutrinos. That's beta decay (as in radioactivity).

I have been wondering however, what the smallest possible mass for a particle as predicted by E=mc^2.
If m = E/c^2, and we let E = whatever one quantum is in Joules, doesn't that give us the minimum rest mass in kilograms of any particle? (if c is 300,000m/s). And does this value correspond with the current mass of the minimum sized particle?

15. ### vslayerRegistered Senior Member

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4,969
in a way they are topped up, if you get 2 ions of opposite charges(one with less electrons, one with more) they will fuse to make an particle of neutral charge, and when this later separates there are 2 normal atoms left

-1ion + +1ion --> neutral particle --> 2 regular atoms

in order for an atom to lose charge that charge must be taken on by another atom which becomes the negative ion as demonstrated above

mass cannot just dissapear, it has to go somewhere

16. ### rumborakRegistered Member

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Well, quanta don't have a certain amount of energy, they can have any amount (through E = h*Nu), it's just that those amounts come in packages.

There is a quantization of energy hypothesized by String Theory, but that's at values of the Planck energy, which is DAMN small and definitely doesn't correspond to any know particle.

rumborak

17. ### cckieranHighSchool Phys/Chem studentRegistered Senior Member

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Ah, didn't know that. Thanks.

Ok, so do we have evidence to suggest that quarks are elementary particles?

18. ### gentleRegistered Senior Member

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I have not read the other replies yet. Could an object give of quanta of energy and remain the same size. I went the bathroom this morning and I am still six feet tall, My mass has decreased slightly but my belly still looks the same. Now I Just thinking outloud but maybe it could be an ever small change in density and mass but not volume.Mass= density times volume?

19. ### cckieranHighSchool Phys/Chem studentRegistered Senior Member

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An atom doesn't need to lose mass to emit energy.
Let's use an examply of fluorescent lights:
Electrical energy is absorbed by the electrons of atoms in the gas tube. When they absorb this energy they change to higher energy orbits. In this excited state, they are not stable, so they emit the extra energy in the form of photons and move back to their ground state.