Coordinate bonds (2 Viewers)

[ZZZZZZ]

correct me if i'm wrong, when non metals undergo cordiante bonding one of the atoms end up with 10 out electrons instead of 8.....

 

[hsc=suicide]

correct me if i'm wrong

if no one answers, are you right?

 

[tristambrown]

NOOOOOOO
thats the point of it being in the syllabus id does not bond like a regular covalent bond

 

[tristambrown]

now that ive quickly dispelled that i'll try to do some ascii lewis diagrams lol

also keep in mind that while oxygen likes 8 electrons to fill its shell other atoms are different and may have different config's (there are things on the net to help u work these out after the exams if yur interested - we are not expected to know this for any atom other than Oxygen)

Normal covalent bonds share electrons between atoms .. with co-ordinate covalent bonds one atom donates BOTH the shared atoms & the other greedily accepts without giving any back

.....X.X.........................................X.X
X....O ...X-----shared------------X....O ...X
X..........X------Shared-----------X..........X

O2
Both oxygens get their full (8 electrons) in normal covalent bonding


Co-ordinate is different

.....X.X.........................................X.X................................X.X
X....O ...X-----shared------------X....O ...X---Shared----------O....XX
X..........X------Shared-----------X..........X---Shared------......XX (not shared)

O3

the third oxygen "borrows" 2 electrons from the one in the middle but does not share any of it's own. This is co-ordinate covalent bonding.

O2 and O3 are allotropes of oxygen (different forms of the same element)
(just as carbon and diamond are both allotropes of carbon - same stuff but very very not)

 

[dral]

i find crappy paint drawings more easy to read and definitely more informative about my status

 

[phil2010]

correct me if i'm wrong, when non metals undergo cordiante bonding one of the atoms end up with 10 out electrons instead of 8.....

Sorry to say this, but you might be mistaken.
A co-ordinate covalent bond is a shared pair of electrons (like a normal covalent bond) ... BUT ... both electrons come from only one of the 'atoms' being joined. In a 'normal' covalent bond, each 'atom' supplies one electron each to the "shaired pair of electrons".

I'll give you two examples, where the "octet rule" applies.

1) H2O + H+ --> H3O+
The oxygen in the water molecule has 4 pairs of exectrons - two pairs are bonded to the hydrogens (each pair consists of 1 electron from the oxygen and 1 electron from the hydrogen). There are also two unbonded pairs of exectrons. In this state the molecule is electronically stable as each hydrogen has 2 electrons (one pair) in its outer shell (1st) and the oxygen atom now has 8 electrons in its outer shell (2nd). The whole molecule is electronically stable and overall (electronically) neutral.

Along comes a H ion - with no electrons. It can "latch onto" one of the unbonded pairs of electrons around oxygen. This 'new' hydrogen now has 2 electrons in its outer shell and oxygen still has 8 e- in its outer shell. As we have added another proton (= hydrogen ion) the particle, H3O, now has an overall positive charge, H3O+

Try this one.
2) NH3 + H+ --> NH4+
In the ammonia molecule, NH3, the nitrogen has 8 electrons in its outer shell, 4 pairs of electrons; 3 bonded pairs and one unbonded pair. Its the unbonded pair that the hydrogen ion uses ("shares") with nitrogen to form the ammonium ion. Note both electrons were 'donated' from the nitrogen - none came from the H+.

Hope this helps.