Molecular Forces

Tim Robbins

Hi,
The force of gravity is very weak at molecular and atomic level and can be neglected.
Can anybody tell what forces (Nuclear or Electro Magnetic) hold an atom together, make an electron spin around the nucleus at a certain distance and work at a molecular level?
Thanks

Tim Robbins

Hi,
some more info here:

http://www.wsu.edu/DrUniverse/gravity4.html

The strength of the electrical force is measured by a constant equal to 9.0 x 109 N-m2/C2. Gravity is measured by a gravitational constant equal to 6.67 x 10-11 N-m2/kg2.

Got that? Well, hang with me. We’re getting to the punch line.

Professor Collins says that if you combine those constants with the mass of a proton (1.67 x 10-27 kg) and charge of a proton (1.60 x 10-19 Coulomb), you can show that the electrical force is 1 x 1036 times stronger than gravity.

Anybody know the Maths in between?
Thanks

Son Goku

The force that holds a proton or a neutron together internally is the strong nuclear interaction, mediated by gluon exchange between quarks. The energy of the exchanged gluons is responsible for most of the mass of the proton and neutron.

The force that holds the protons and neutrons to each other to form the nucleus is a residual side-effect of the strong nuclear interaction and is mediated by pions.

What holds the electron to the nucleus is the electromagnetic interaction and is mediated by photons.

Finally, atoms are held together to form molecules by combining their hold on each other's electrons (called covalent bonding) or exchaning electrons which results in them gaining a net charge and attracting each other (ionic bonding).

The derivation in your second post can be filled in by using the expression for the electric field of a single charge (given by Coloumb, occasionally called Coloumbs law) and the expression for the gravitational field of a single object given by Newton.

Tim Robbins

Son Goku wrote: »

Finally, atoms are held together to form molecules by combining their hold on each other's electrons (called covalent bonding) or exchaning electrons which results in them gaining a net charge and attracting each other (ionic bonding).

The derivation in your second post can be filled in by using the expression for the electric field of a single charge (given by Coloumb, occasionally called Coloumbs law) and the expression for the gravitational field of a single object given by Newton.

Hey thanks for that. Basically reading Martin Rees Just Six Numbers for the fourth time trying to make sure I understand ever thing and so I don't have to read it again!

So, two hydrogen atoms form a molecule. The electro-magnetic force of attraction is each atoms electron to the other atoms proton? Is this correct?
Thanks

Son Goku

Tim Robbins wrote: »

Hey thanks for that. Basically reading Martin Rees Just Six Numbers for the fourth time trying to make sure I understand ever thing and so I don't have to read it again!

So, two hydrogen atoms form a molecule. The electro-magnetic force of attraction is each atoms electron to the other atoms proton? Is this correct?
Thanks

Yes, hydrogen atoms form covalent bonds. This is basically, as you said, each atoms electron being attracted to the others proton.

If you are a little familiar with Quantum Mechanics, then more accurately what happens is that the electromagnetic field caused by both protons causes the probability cloud (wave function) of each atoms electron to change from being a spherical cloud enveloping one atom, to being a ellipsoid shaped cloud covering both atoms.

Tim Robbins

Son Goku wrote: »

Yes, hydrogen atoms form covalent bonds. This is basically, as you said, each atoms electron being attracted to the others proton.

If you are a little familiar with Quantum Mechanics, then more accurately what happens is that the electromagnetic field caused by both protons causes the probability cloud (wave function) of each atoms electron to change from being a spherical cloud enveloping one atom, to being a ellipsoid shaped cloud covering both atoms.

Very good. I did Electronic Engineering in Trinity over 10 years ago and we covered a lot of this stuff. It was very poorly explained. You'd be a very good lecturer.