ions (to do with atoms)

[tommy666]

k i know what an atom is made up of. i know that the electrons on the outer shell of an atom are the ones with the most energy and so they are the only ones that can be transferred (what is this process actually called? transferring of electrons?) to another type of atom. what tells you whose atom's electrons switch round? is it all of the electrons on the outer shell of one atom that move to the other, or does it differ? if so, what are the rules and why? what are the rules for which atom gives up its electrons, and why? is it something to do with balancing, and heading towards certain numbers of electrons? if so, what happens if they would both get closer to the number by giving up their electrons? say the balance number is 8, you have an atom of 20 electrons and atom of 30 electrons, and one of them becomes an ion. what happens? also, what is the process that makes them become ions? why does it happen, and what use do we have for this? if u can answer any of these questions id be grateful. ty

[MrPahoehoe]

As you might expect this a very complicated issue...and to be honest i don't really know that much. I do have a few points though.

The process of losing/gaining electrons is called Ionisation.

As you pointed out electrons form 'shells' around the nucleus of the atom. Once one shell is full, the next electron will form another shell (outer shell). The atom is more stable if it has a full outer shell. Ionic bonding is when different elements exchange electrons to attain a full outer shell. Other factors can cause ionisation, these ions may not have a full outer shell (i think if you had enough energy you could completely strip an atom of all of its electrons).

The type of substance will control how many electrons are lost/gained. Group 1 metals (first colum in the periodic table, eg Sodium) are in group 1 because they have 1 electron in their outer shell. They will loose 1 electron to become ionised. Chlorine is in group 7 and...yes you guessed it: 7 electrons in the outer shell. Chlorine will gain an electron to get to a full outer shell (gaining one is easier than loosing 7).

A normal atom will have the same number of electrons (negative) & protons (positive). When sodium looses its outer electron it becomes a positive ion (cation). Vice versa chlorine will become negative (anion). These charged ions would attract each other. If the sodium had lost its electron to chlorine then these ions would be in an ionic bond forming a molecule of NaCl (sodium chloride).

Oxygen is in group 6, so it needs 2 more electrons to get to a full outer shell of 8. It would bond with sodium, but as sodium would only relinquish 1 electron it would take 2 atoms of sodium for every atom of oxygen.

......

[MrPahoehoe]

...continued

Examples of complications are that the first shell only has 2 electrons not 8 (hydrogen & helium) and the later shells may have more than 8 electrons & sub-shell divisions. But its easier to explain will elements that have 8.

Pretty much all of 'chemistry' is driven by atoms trying to become stable by getting a full outer shell of electrons: this can happen in other ways: for example in covalent bonds the two atoms will share the electrons rather than exchanging them. The confusion comes from the fact that no bond is 100% covalent or ionic there is a aspect of both in any one bond.

[elginsmarble]

The process of losing an electron is called ionisation and gaining an electron is called an electron affinity.

The point is to balance the charges between the reacting metal and non-metal to form a neutral and stable compound as the product.