how do the atoms/molecules in a solid stick together?

[paul]

i know that the atoms/molecules in a solid are less energetic than those in a liquid, and therefore vibrate less, and are hence 'solid'

 

but i don't know how these "less energetic" atoms/molecules stick together

[Gilded]

Ionic configurations and the van der Waals force come to mind.

[insane_alien]

gilded has it.

 

its all electrostatic forces. there are a few types of bond that are different.

 

1/van der waals attraction. not really a bond just a weak force of attraction between the atoms but can be enough to cause the substance to solidify.

 

2/ covalent lattice(diamonds are an example of this) can be very very strong, infact the hardest subsance on earth has this type of bond keeps it solid to very high temperatures. caused by the atoms sharing electrons in covalent bonds.

 

3/ Ionic lattice, again, very strong bonds, typically high melting points caused by electrostatic attraction of oppositle charged ions. basically van der waals on steroids.

 

4/ metallic bonding. electrons become delocalised and hop from atom to atom freely.

[CaptainPanic]

It's not so much the question what holds solids together, it's the question what holds all matter together.

 

Atoms and molecules are always attracted to each other... also in the liquid and even gas phase. When they have less energy for moving, then these attractions become more important.

 

It's probably best to investigate the list that insane_alien has given. Wikipedia will certainly have a page about all 4 forces.

[paul]

thanks.

 

i have read up a wee bit on it, but i'm still not sure i'm there yet. take NaCl. first of all the Na donates an electron to the Cl atom, so they now both have full outer shells; they're "happy". so why does one NaCl molecule 'link up' with another?

 

A. intermolecular forces? van der waals attraction ('not really a bond, just a weak force of attraction')? electrostatic forces?

 

captainpanic, you mentioned the four forces; i have asked myself which of those it is, and the best candidate seems to me to be the electroweak force; but that force is responsible for an electron being attracted to a proton (opposite charges attract); an NaCl molecule isn't opposite to another NaCl molecule, is it?

 

if the Na atom donates its valence electron to the Cl atom, they both have full valence shells; they're both happy. then they 'hook up' because one is a cation, one is an anion. why isn't that the end of it?

[Kyrisch]

That is it. They stick because one is positively charged and the other is negatively charged. Why does this form a solid? Put a mole of these pairs together and they will form a three-dimensional checkerboard configuration with alternating anions and cations. This is your solid table salt. Each and every cation is attracted to each and every neighbouring anion.

[insane_alien]

thanks.

 

i have read up a wee bit on it, but i'm still not sure i'm there yet. take NaCl. first of all the Na donates an electron to the Cl atom, so they now both have full outer shells; they're "happy". so why does one NaCl molecule 'link up' with another?

 

this would be the ionic bonding i mentioned in my post.

 

captainpanic, you mentioned the four forces; i have asked myself which of those it is, and the best candidate seems to me to be the electroweak force; but that force is responsible for an electron being attracted to a proton (opposite charges attract); an NaCl molecule isn't opposite to another NaCl molecule, is it?

 

there is nothing as exotic as the electro weak force here. that only occurs in high energy physics. much higher than anything you will encounter outside a particle accelerator or supernova.

 

if the Na atom donates its valence electron to the Cl atom, they both have full valence shells; they're both happy. then they 'hook up' because one is a cation, one is an anion. why isn't that the end of it?

 

that is the end of it, you are over complicating things.

[farmboy]

thanks.

 

i have read up a wee bit on it, but i'm still not sure i'm there yet. take NaCl. first of all the Na donates an electron to the Cl atom, so they now both have full outer shells; they're "happy". so why does one NaCl molecule 'link up' with another?

 

The reality of the bonding is no where near as simple as that. Sharing electrons is more like a model that gives us generally the right answers, and allows us to start understanding chemistry but isn't real. You have to remember that the atoms don't really look the way they are drawn, with a shell convienently missing an electron and another atom that just happens to have another one that matches up nicely. The atoms are three dimensional and have three dimensional electron clouds. Each Cl is bound to 6 Na's and vice versa forming a lattice. The charge is stabilised over the whole lattice. Even that doesn't really tell us what is going on. To get the true picture you would need to describe the system quantum mechanically, which I probably couldn't do myself, and besides, unless you understand quantum mechanics yourself that answer probably won't be any more fulfilling than sharing electrons.

 

A. intermolecular forces? van der waals attraction ('not really a bond, just a weak force of attraction')? electrostatic forces?

 

captainpanic, you mentioned the four forces; i have asked myself which of those it is, and the best candidate seems to me to be the electroweak force....

 

I'm pretty sure he doesn't mean the four fundamental forces, just the four forces mentioned previously in the thread. He was saying tht Van der waals are weak intermolecular forces, not that they were the weak (nuclear) force.

Edited December 4, 2008 by farmboy

[Riogho]

When you guys say "Van Der Waals" attraction are you talking about the London Dispersion Forces, or is that different?

[farmboy]

When you guys say "Van Der Waals" attraction are you talking about the London Dispersion Forces, or is that different?

 

I think the term van der Waals applies to a few different types of intermolecular attractions, of which the london dispersion force is one. I don't think that name is used very often though, they are generally called instantaneous dipole induced dipole forces, which is a much better name as it basically ''does what it says on the tin.''