could somebody explain clearly how to make chemical formluas/ ionic formulas (whats the difference?)? i dont understand what oxidation number to use when bonding 2 elements, whats the difference is with the number of that element and the “chare it has is, and what to do with oxygen is added to it all like sodium phosphate. please explain it as clearly as possible and thanks in advance these concepts are very confusing to me. =]
Start with the simple stuff – elements ALWAYS have zero charge
Oxygen, with very few exception, is always -2 (the exceptions are peroxides and superoxides)
Hydrogen is always +1 (the exception is hydrides)
Halides (F, Cl, Br, I) are -1
Alkali metals (Li, Na, K, etc.) are +1
Alkali earth metals (Be, Mg, Ca, etc.) are +2
No, for a complex molecule like carbonate sodium carbonate (Na2CO3), you can easily figure out the charge on the C by adding it all up
3 O’s means -6, but that’s offset by 2 Na’s, so you have to balance the remaining charge (-4) with the charge on the C, hence, +4
Same for phosphate — let’s stick with a simple one, sodium phosphate Na3PO4. O’s are -8, Na’s are +3, so the P must be +5
When all you have is the ion – like sulfate (SO4), you need to either be told the charge or know the net charge. Sulfate as a whole is -2. The O’s are -8 so in order to have a net charge of -2, the S must be +6.
Good luck
chemical formulas and ionic formulas are just different types of formula for different types of compounds.
See here http://au.answers.yahoo.com/question/ind…
for a detailed explanation of the difference between compound types.
Chemical formulas are used where the base unit is a discrete molecule, e.g. H20. Ionic formulas are used where there isn’t a base unit, just a ratio of one element to another, e.g. NaCl or CaCl2 as the whole substance is a lattice, rather than a collection of molecules.
“Charge” is the overall measure of how electronegative an atom or molecule is (the result of the balance between the +ve protons in the nucleus and the -ve electrons around it.)
Charge is a measure of what state the atom/molecule is in *now*.
The oxidation state of an element is how many electrons have been taken away or are ‘missing’ from it. All single atoms will have a ’standard’ oxidation state that they are normally found in, only noble gases have a ’standard’ oxidation state of 0, as they are the only ones with a ‘complete set’ of electrons (this is why they don’t react).
So oxidation state is a measure of what has *changed* in the atom or molecule.
In a single atom or element, the charge and the oxidation state will be the same. In a compound they will be different. E.g. an element that has lost two electrons and then formed a bond with another element that had two electrons to spare.
The new compound will have an overall charge of 0 (neutral) as the charges balance out. However, the original element (just the element, not the compound) is still in an oxidation state of 2+ as it had to lose two electrons to get to the point where it is now in the compound.
For elements that naturally occur in different ionic forms, such as iron (and most transition metals), knowing the oxidation state will tell you which ion you were originally dealing with (i.e. Fe^2+ or Fe^3+).
This site gives a fairly good explanation of how oxidation states work in equations.http://www.chemguide.co.uk/inorganic/red…
Compounds like phosphate, sulphate and carbonate are fun because although they are actually molecules themselves, they act as single atoms when bonding with other atoms. Consequently they have their own charges and oxidation states.
To sort out where you’re getting confused with actual equation problems, it would probably be best if you posted some of the problems you’re trying to solve.
Hope this helps, you can email me if you’re still stuck!