Where did those definitions come from?

Celina wrote:

An atom is the smallest, indivisible, indestructible, uncharged particle of an element that can take part in a chemical change.

If you include nuclear chemistry, then atoms are very much destructable. And it can be quite easy to take an atoms electrons, making it somewhat divisible. A better definition is: "the smallest component of an element having the chemical properties of the element."

An ion is an electrically charged particle that can take part in a chemical change.

Take an electron off or put an electron on an atom or molecule and you have an ion.

A molecule is the smallest uncharged particle of an element or compound that can exsist on its own.

Molecules can be charged. A better definition: "the smallest particle in a chemical element or compound that has the chemical properties of that element or compound."

So what is a particle?
Is a molecule an atom that can exsist on its own (that's what I got from the definition above.)?
I'm not quite understanding this.(If any definitions above need correction please do so.)

Some elements can exist on there own, some can not. Oxygen for example exists as . A particle is just a chunk of stuff. It like saying "the smallest thing in a chemical element or compound that has the chemical properties of that element or compound."

Celina wrote:

So what exactly is the difference between an atom and a molecule?

Is it that a molecule can exsist on its own and an atom cannot?

Some atoms can exist on their own. Actually, pretty much all of them can depending on the environment in which you find them. (although there are plenty that do not occur naturally (we have to make them.)

An example:

Water is made up of two elements: hydrogen and oxygen. is a molecule. Your glass is filled with trillions of them, and they are all interactings with each other. If I wanted to replicate a glass of water (like on Star Trek) I would only have to make 1 molecule and copy it billions and billions of times. The molecule is the smallest chuck of stuff in water that still has the same properties as water.

Now of course I can break into smaller pieces:



and are ions. These ions come from the atoms O and H.

Here is were your teachers first definition breaks down. An element is defined by the number of protons it has. A hydrogen atom has 1 proton. In the above example, I have . This also has 1 proton, therefore it is still the element hydrogen. It is also smaller since it is missing an electron. I can make through very simple chemical means (acid/base reactions for example), and it takes part in chemical changes all day long.

So what is the atom? H or ?

I don't really know. As the definition of "atom" is pretty loose. I can strip electrons off of, say, sodium (Na) all day long by chemical means. So from what most definitions tell us, the Na would be composed of 11 protons, 11 neutrons and ZERO electrons, since this would be the smallest. It's pretty darn hard to get all of those elctrons off of Na, but not hard at all to get them off of hydrogen.

In general, when you discuss different atoms, you normally care about the number of protons. That is what ultimately distiguishes one atom from another.

Ions depends on how many electrons the atom has (more or less than the number of protons).

And usually molecules are made up of several atoms.

Celina wrote:

So a molecule is made up of atoms of the same element and an element is made up of molecules of the same element.

So it's something like: atom- molecule- element.

No. Molecules can be made up of many different elements. I gave the example of which is a molecule composed of the elements hydrogen and oxygen.

You can also have molecules that are made up of several of the same elements, such as , which is made up of two oxygens. If you were to buy a tank of pure oxygen, you would be buying , since naturally, we normally find oxygen in what we call it molecular form. But you can have what is called elemental oxygen which is just O.

In general, basic chemistry, the term atom and element are used interchangeably. Such as: an atom of oxygen is made up of the element oxygen.

okay, i think i get it. Thanks!!!!

Last edited by Celina (2006-03-07 02:27:08)