chem 一連串ge bonding 問題

1. all covalent bonds have directions; all ionic bonds have no directions.

in ionic structure like KF, attraction of K(+) to F(-) is in ALL directions. all surrounding F(-) ions are attracted to that K(+), no matter they're on which direction. thus ionic attraction is "non-directional", or to say, omni-directional.

in covalent structure like silicon dioxide SiO2, attraction of Si does not direct to all atoms around, or even not to all oxygen atoms around. the attraction only directs to 4 specific surrounding oxygen atoms. on the other hand, attraction of O does not direct to all atoms around, not even all silicon atoms. instead, it only direct to 2 specific silicon atoms.

the attraction in SiO2 is directed along the covalent bond. then it has direction.


2.
don't understand. all cations must exist in pairs with anions. how's it related to dative covalent bond?

btw, ozone contains dative covalent bond, and it can exist on its own.


3.
of course not!!
magnitude of charge of ions are not necessarily the same. for example, sodium ion has 1+, while oxide ion has 2-. to balance the charge (a compound is totally electrically neutral). in sodium oxide, no. of sodium ion is twice of oxide ion.


4.
Ｏ＝Ｏ→Ｏ
of course the molecule is in V-shape. bond angle is approximately 120 degree.


5.
electrons repel each other. why would an atom holds the electrons in shells even they repel each other? why electrons will stay around the atom and other electrons?
why atoms will form covalent bonds? in a bond there're two electrons. wouldn't they repel each other? why wouldn't the nuclei of two atoms will repel each other?



2010-10-17 04:29:27 補充：
the fact is, nucleus is positive and attracts electrons around it, such that electrons stay there. same applies to covalent bond.
two nucleus repel each other. but like a sandwich, shared electrons between two nuclei are attracted by the nuclei on both sides -- in both directions.

2010-10-17 04:29:44 補充：
thus two nuclei indirectly attract each other. we consider subatomic level in covalent bonds.

in ionic bond, we usually don't consider this effect. ions with opposite charges already attract each other. we consider "ion" -- atomic level as a whole.