Bonding

1. Not all solids are covalent compounds. e.g. salt, by definition, is the product of neutralization. So salts can only be ionic compounds (consisting of cations and anions). Sugar, on the other hand, are covalent compounds.
2. C-H bond is covalent bond, formed by sharing of electrons. C and H each contribute 1 electron for sharing and form a single bond. They are electrically neutral.
3. Glucose (C6H12O6 ) is a covalent compound. It is a solid at room temperature and pressure but this has nothing to do with the strong, intra-molecular covalent bond. Instead, it relates to the inter-molecular van der Waals force (which generally increases with molecular size) and also hydrogen bonding (not for every covalent compound).
For a covalent compound to change from solid to liquid state, energy is needed to overcome van der Waals forces (and hydrogen bonding in some cases) between molecules, NOT by breaking covalent bonds between atoms in the molecules. (A compound is decomposed, not melted, if covalent bonds are broken)
The case for ionic compounds is different. To change ionic compounds from solid to liquid state, ionic bonds between cations and anions have to be overcome. Lots of energy is required to break strong ionic bonds and thus ionic compounds normally exist as solid at room temperature and pressure.
4. Many compounds, both ionic and covalent, do not contain any oxygen or hydrogen atoms, e.g. Sodium chloride (NaCl) and tetra-chloromethane (CCl4).
5. Oxidation number applies to every atoms in every compound. It has nothing to do with the existence of hydrogen or oxygen atoms.

2007-12-04 20:57:04 補充：
all elements in a compound must be over or below 0 of the oxidation number? - Yes. elements only have 0 oxidation number in their elemental state.

2007-12-04 20:57:57 補充：
Compounds may be formed by reactions between more than 1 elements. They may also be formed by reactions between element(s) and compound(s) or between different compounds. i.e. :

2007-12-04 20:58:16 補充：
1. Element A + element B => compound(s)2. Element + compound => compound(s)3. Compound A + compound B => compound(s)For 1 & 2, there must be a change (increase/decrease) in oxidation number of the element(s) and thus must be a redox reaction.

2007-12-04 20:58:26 補充：
For 3, it may or may not be a redox reaction. e.g. acid-base neutralization gives salt and water but it is not a redox reaction as there is no change in the oxidation number in all participating elements.

2007-12-06 23:50:41 補充：
Yes, in a compound, there must be both atoms with positive and negative oxidation numbers.For mono-atomic ion(s) in ionic compounds, oxidation number = charge on that ion(s).

2007-12-06 23:51:58 補充：
For covalent compounds and atoms in poly-atomic ions, we ASSUME (i.e. not real) that they form ionic bonds and in making such assumption, we further assume that the more electronegative atom gets the electron(s). Their oxidation number then = HYPOTHETICAL (again, not real) charge on each atom.

Are all solids(non-metal non-metal compounds) are formed as covalent bond?

-- No, e.g. dry ice solid CO2. Solid is a state of a substance only.

How about solid salts?

-- Most if them are formed by ionic bonds.

How about C-H?

-- Covalent bond

Is C here = -1 and H here is +1?

-- Not exactly -1 and +1, it depends on what other bonds with carbon.

How about sugar? Like glucose is solid. Is it bonded with covalent bonds?

-- The atoms of a Glucose molecule (a single molecule) is covalent bonded, but glucose (the whole, e.g. the one you can buy from the supermarket) is not, they are bonded by hydrogen bonding.

Are there any compounds (at all states, liquid, solid...) are made out of non-oxygen nor hydrogen?

-- Yes, e.g. I2, iodine

Does oxidation number apply to a compound like this?

-- May not.

2007-12-04 14:12:43 補充：
Typos in line 4.-- Most of them are formed by ionic bonds.

glucose is a ring structure bond with ether group. Of course it is a covalent bond compound.
Unless the compound have charge (+/-) , otherwise, it is covalent bond.
CH bond is not (-1 C) bond with (+1 H) , it is just electrostatic nature eletron sharing. The overlapping of the specific electron orbitals between two atoms can form a covalent bond.

compound made out of non O nor H. eg: CCl4 Br2 ,
Oxidation number : i don't know at all....