f3 chem bonding (uegent)

i've to praise you for your curiosity and detailed observations.
but first of all, you've mis-spelled "silicon" as "sikicon". even so, that's NOT silicon. "S" is sulphur.

both questions are too much for a f.3 student. they're actually too much for old CE students. anyway i'll try to explain briefly.

1.
dotted line can be read as "half-a-bond". a C-O bond is not Localized between C and a specific O atom; instead, this bond can "drift" and goes around.

When the bond goes to an O-atom, the negative charge goes to another O-atom [which has a single bond only]. this is called Delocalization of (bonding) electrons. since the bond can freely goes around, it is "shared" by two O-atoms "half-by-half".

2.
starting from aluminium, elements do not strictly follow octet rule. some elements may, some may not; some compounds of an element may, some may not. sulphur is one of these elements. sulphate ion is one of these "complicated" compound / ion.

put it in this way... the S-atom does not 2- charge. it can be considered to be "6-electrons have lost". [refer to chapters on Redox -- Oxidation Number] . even so, S-atom can maximally accommodate 18 electrons.

...... this is complicated to explain, but a lot of ions act like this. in old CE exams, this phenomenon will NOT be taught or examined. this is taught in A-level, related to actual structure of atoms ad electron shells. if REALLY interested, try searching "s-p-d-f" subshells.

go to this website (ChemGuide) and look for titles of "atomic structure" and "inorganic chemistry". it's about UK's A-level chemistry.


2010-09-19 22:45:19 補充：
non-octet structures are common.