One for FWL - Quantum Physics

[mildmanneredjanitor]

FWL, Just read your profile, interest etc.

Maybe you can answer me this one (I'm a bored insomniac with an overactive mind!)

As I remember, the structure of an atom comrises a nucleus with a number of neutrons/protons revolving around it??? The number of netrons etc. determining the type of element (atomic number etc.???)

These neutrons/protons are revolving at speed? so what prevents them from shooting off under centrifugal force and if there is attracting force preventing this, how is it all kept under balance???

Also, if the atom is complex, how are all the revolving parts kept in syncronistation?? Or are they?? Or is it the colliding of the 'parts' that give rise to radiation with radioactive elements???

I think I've prattled on enough now...

If only science was made interesting at school...

 

[ban-all-sheds]

Not 100% correct.

The nucleus is comprised of protons and neutrons. The orbiting particles (or are they waves?) (or both??) are electrons, and there are (depending on the atomic number of the element) more than one set of orbits (or shells) of different energy levels.

Are the electrons orbiting at speed? Possibly, or do they just appear and disappear? Ah, now there's a thing.

What holds it all together? Strong interaction, weak interaction..

I suspect that not even FWL's prowess extends to an explanation of particle physics that would comfortably fit into a post on this forum.

You could try this search which will get you shed-loads of material to read, much of which will provide all of the answers that are currently known. Or postulated. Or argued about.


PS - there is no such thing as centrifugal force.

 

[securespark]

Try telling that to the manufacturers of centrifuges.

 

[ban-all-sheds]

Ah - I never claimed that there was no such thing as a centrifuge, just no such thing as centrifugal force.


Although if I was being very pedantic I might insist that the manufacturers rename their machines to "centripetes"...

 

[Big_Spark]

Well here goes.

BTW, this is Particle Physics not Quantum Physics. The Latter deals with the subatomic level below that of Protons and Neutrons.

As Ban said, the atomic mass of an atom is a product of its Neutron/Proton mass, ie; the number of neutron and protons forming the nucleus. The Isotopes of a given element are decided by the number neutrons in the nucleus. The Atomic element is decided by the Proton Mass of the Nucleus.

Example:

Hydrogen has 1 Proton and 1 Electron
Deuterium has 1 Proton 1 Neutron and 1 Electron
Tritium has 1 Proton 2 Neutrons and 1 Electron

Helium has 2 Protons 2 Neutrons and 2 Electrons
Helium 3 has 2 Protons 3 Neutrons and 2 Electrons.


The Proton and the Neurton both have Mass, however the Neutron is the most massive particle making up an atom.

The Protons and Neutrons are bound together by The Strong Nuclear Force, this is the force that must be overcome to either create a Fission or Fusion reaction. The Strong Nuclear Force only operates at very short distances, typically less that the width of the nucleus of a given atom, however it works as all the Protons and Neutrons are close enough for it to operate. The force is strong enough to cause all the protons and Neutrons to move as one, they do not move independantly within the atom.

This force also has a weaker brother, the Weak Nuclear Force, this operates over longer distances and it is this force that binds Electrons to atomic nuclei.

An Atom will normally contain as many Electrons as it contains protons, arranged in orbits around the nucleus, but not like the planets of the solar system, more like a cloud of particles in stable orbits.

As the Electrons orbit further from the Nucleus the force acting upon them gets increasingly weaker. In metals and other conductive materials, the outer part of the cloud are bound so weakly to the nucleus that they can be easily knocked off their orbits, either into the atom or away from the atom. These electrons are called VALENCE Electrons, and it is their movement between atomic neuclei we observe as Electricity.

All atoms can have electrons stripped from their outer shell if they are bombarded by electrons, protons or other high energy sources, when this occurs the atom is said to be Ionised, if it has lost electrons, then it is Negativelt Ionised, if it has had extra Electrons forced upon it, it is Positively Ionised. Ionised particles can also be ionised further by the same process..

These Ionised atoms are controlable by magnetic fields, and they can be formed into clouds of Ionised gas called Hot or Cold Plasma.

Regarding the Actinide Series and other Radioactive elements, these are radioactive because they are unstable. Nature likes order and balance, but many Isotopes of many elements are not in balance, the forces in their heart are unbalanced. This causes neutrons, protons, high speed electrons or even Helium nuclei to be emitted from the core. As time passes the element slowly changes it's atomic weight and stabilises. The time it takes for 50% of a given mass of a Radioactive element to decay into a stable element is called it's Half-Life, this can range from nano-seconds to billions of human years.

For Reference:

Alpha Particle are Ionised Hydrogen Nuclei..a single proton.

Beta Particles are Electrons or Positrons ejected from the heart of the atom, usually as a by-product of the formation of Ionised Helium Nuclei during the radioactive decay of the nucleus.

X-Rays and Gamma rays are photonic in nature and will behave as a particle or a wave, there is a debate going on as to whether they have mass.


Did this answer your question ok?

 

[pipme]

Centrifugal force is actually not a force but the experience of an inertial force experienced in a rotating reference frame acting away from the center of the rotation. It is equal in magnitude but opposite to the centripetal force required to constrain the body to move in a circular motion.

P

 

[journeyman]

Beta particles are high energy electrons or positrons. I did not know that the nucleus of a helium atom was formed formed from such particles.

It's physics Jim, but not as we know it.

http://en.wikipedia.org/wiki/Beta_particle

 

[Big_Spark]

Any motion in a curved path represents accelerated motion, and requires a force directed toward the center of curvature of the path. This force is called the centripetal force The name comes from the Greek for "center seeking" force.

The centripetal acceleration can be derived for the case of circular motion since the curved path at any point can be extended to a circle.

Note that the centripetal force is proportional to the square of the velocity, implying that a doubling of speed will require four times the centripetal force to keep the motion in a circle. If the centripetal force must be provided by friction alone on a curve, an increase in speed could lead to an unexpected skid if friction is insufficient.

Centripetal Force is calculated thus F= m(v*2/r)

Centrifugal force does not exist. It is a fictitious force that can be thought of as acting outwards on any body that rotates or moves on a curved track.

Newtons First Law states

Any object in a state of rest or of uniform linear motion will remain in such a state unless acted upon by an unbalanced external force.

So if a body is moving its natural tendency is to continue moving in the same direction in a straight line, forever. No external force is required to keep it moving in that straight line at that speed. Only the application of some force can change the speed or direction of movement.

It is this that gives the "impression" of a Force acting upon a body that is in circular motion. A good example is a child on a roundabout, Centripetal force is provided by the child holding onto the roundabout, this keeps the child moving in a circular path with respect to the environment. However if the child lets go, the natural tendency is for their body to continue, in a straight line, in whatever direction the child is facing at the moment they released their grip. This is the First Law in action, and there is nothing the child can do about it.

Centrifuges use this principle of the First Law to impart energy into items or matter within them, it is easier to call them Centifuges than First Law Obeyers!!!

 

[Big_Spark]

-double post

 

[Big_Spark]

Beta particles are high energy electrons or positrons. I did not know that the nucleus of a helium atom was formed formed from such particles.

It's physics Jim, but not as we know it.

http://en.wikipedia.org/wiki/Beta_particle

Corrected my post, I have worded it wrong which gave the wrong impression...Thanks for the heads up.

 

[ban-all-sheds]

Centrifugal force is actually not a force but the experience of an inertial force experienced in a rotating reference frame acting away from the center of the rotation. It is equal in magnitude but opposite to the centripetal force required to constrain the body to move in a circular motion.

P

No.

 

[Big_Spark]

NO? Care to expand, which bit of his post are you saying no too?

 

[mildmanneredjanitor]

A good example is a child on a roundabout, Centripetal force is provided by the child holding onto the roundabout, this keeps the child moving in a circular path with respect to the environment. However if the child lets go, the natural tendency is for their body to continue, in a straight line, in whatever direction the child is facing at the moment they released their grip. This is the First Law in action, and there is nothing the child can do about it.

Ha Ha Ha Ha!!!!

'Argh, Dad, do we have to help you with your experiments again!'




BTW, This is all great stuff, trouble is, it creates more questions!

Neutrons and protons (are these 'matter'?) and electrons are energy??

Or isn't it this straight forward at atomic level??

Is the weak nuclear force related to gravity???

 

[Big_Spark]

Neutron and Protons are MATTER, electrons are MATTER, however they are also made up of energy.

One thing worth remembering is that if you combine a proton and an electron you get a neutron.

Both the weak and strong nuclear forces are related to elctromagnetism and possibly to gravity, although the link has not been established conclusively and some dispute this connection. (The ones who can't do the math )

 

[ban-all-sheds]

NO? Care to expand, which bit of his post are you saying no too?

All of it, i.e. its overall meaning, if it has one.

Centrifugal force is actually not a force

Then it's not a force. So if it is not a force, there can be no such thing as "centrifugal force"

but the experience of an inertial force experienced in a rotating reference frame acting away from the center of the rotation.

If that means that people interpret the feeling of the car door forcing them "inwards" as a force acting on them "outwards" towards the car door, then that is just a perception that arises because they are inside a frame of reference which is being accelerated.

It is equal in magnitude but opposite to the centripetal force required to constrain the body to move in a circular motion.

If you have two forces equal in magnitude and opposite in direction acting on a body, then that body will not change from its state of rest or uniform motion. Since a body travelling along a curved path clearly is changing from a state of uniform motion, there cannot be two forces equal in magnitude and opposite in direction acting on it.