covalent & ionic bonding....a few simple questions!

[lboogy]

Hi everyone,

 

I've just got a few simple questions regarding covalent & ionic bonding....I hope you don't mind!

 

re: ionic bonding. I've read that if sodium metal (therefore neutral sodium atoms) reacts with water, it will result in sodium + ions by getting rid of it's electron on the outside shell. But where would that electron go? The hydrogen and oxygen are already convalently bonded so they have no need to acquire that extra electron to fill up their outer shells. Or would the sodium stimulate the oxygen and hydrogen to break up and create new molecules from sodium, oxygen & hydrogen?

 

re: covalent bonding. If graphite is composed of carbon atoms having 3 covalent bonds - this will not be enough to fill the outside shell so what is the point? If carbon has 4 electrons on it's outer shell, it needs another 4 to fill it. So it already has 4 on the outside shell, it gains 3 more from forming covalent bonds with other carbon atoms. That makes 7, but it needs 8 so there is 1 short. I've read that there are free electrons in graphite. Where do these come from? It appears that there is not enough!

 

thanks for your help in advance

[Rasori]

If I remember my chemistry right, Na is more electronegative than H, it basically swaps out, creating NaO and free H.

 

From what I can tell doing some research on graphite, that fourth electron that you're missing is in a pi bond, connecting the different layers of graphite. I dunno about the free electrons part, but it makes sense that there are some considering graphite is apparently an electrical conductor.

[gonelli]

When the sodium and water react you produce NaOH and H2 gas. The equation for this is...

2 Na + 2 H2O -----> 2 NaOH + H2

So you will have the outer shell electron from sodium being donated to OH, which comes from the water. Because there is only a single bond between O and H, (and O doesn't a full outer shell) it gets the electron from Na. Because there is an extra electron in the OH, it becomes a negative ion. The positive Na and negative OH attract and you get an ionic compound (a salt). And the extra H atoms from the water combine and form hyrdogen gas.

 

As for the graphite what Rasori said is basically right. You have layers of carbon bonded to three other carbons, with the fourth valence electron becoming delocalised and ending up between the layers. They are free to move which is why graphot conducts electricity.

[lboogy]

thanks very much for the help...understood!