dot point blues (1 Viewer)

[fashionista]

hi everee bodee
im makin my summary for chemistry but im havin a bit of trouble putting my thoughts into words for this particular one:

• Analyse the position of these non-metals (which form acidic oxides) in the periodic table and outline the relationship between the position of elements in the peroiodic table and the acidity/basicity of oxides

i kinda wrote the following mumblyjumblynotmakingsensetomebutIknewwutIwantedtosay sentances:

the positioning of elements on the periodic table is such that the electronegativities of the elements increase to the right side of the table. Elements which have a high electronegativites have a positive charge and therefore an excess of electrons, such elements are found to the right of the table and their oxides are capable of donating protons in aqueous solutions. Elements found to the left of the table have low electronegativities and a negatiive charge, in aqueous solutions these element oxides are capable of accepting protons. According to the bronsted-lowry theory acids are molecules which are capable of donating protons and bases are molecules capable of accepting them. therefore the elements from the right side of the table mostly form acidic oxides whereas the elements from the left typically form basic oxides.
does that sound ok or is it makin no sense whatsoever or is it too logn for a summary??
(Ive never done one before and i cant view the ones on this site cuz i dun have zip or sumthing)
luv me!!!!!!!!!!!!!

 

[Ragerunner]

That sounds perfect enough.

Probably want to add there are a few elements which show hey are amopteric - that is they can form both acidic/basic oxides.

 

[ND]

For these kinds of dotpoints, you don't really need summaries, just remember that non-metallic oxides form acidic substances in water (and of course we know that non-metals are to the right of the periodic table).

 

[fashionista]

wowie!!! i got it right????????? *blinks in shock*
so i jus pretty much need to write concise bullet points?
thanx soo much for ur help

 

[Ragerunner]

Yep

They won't ask you a 6 mark question to analyse the posiiton of these metals.

There was one question on this in my HSC, which was in the multiple choice only.

 

[fashionista]

are all the questions straight out of the dot-points? or will they pull one out of obscurity that they shud expect me to be able to synthesise???

 

[Ragerunner]

They expect you to synthesise

It if was straight off the dot points it would be too easy.

/me remembers the BS physics one that looked like Chemistry electrolysis.

 

[jims]

i dont remember ever saying anything about electronegativity for this dot point (although i assume wat u said is correct); ND said all you need for it.

also, atoms are neutrally charged, only ions have a neg or pos charge. an element's electronegativity depends on which route is easiest for it to gain a full outter shell: losing electrons (low electronegativity; metals) or gaining electrons (high; non-metals). it is once it gains or loses an electron than it is charged neg or pos, respectively. i guess this is what you meant but lines like "Elements which have a high electronegativites have a positive charge and therefore an excess of electrons" were confuzalling.

 

[spice girl]

Originally posted by fashionista
Elements which have a high electronegativites have a positive charge and therefore an excess of electrons, such elements are found to the right of the table and their oxides are capable of donating protons in aqueous solutions.

positive charge = excess of electrons??

anyway here's a post-HSC level explanation...that HSC ppl aren't meant to know, but it's nice to know...

anyway...yea it is all about electronegativity, but not directly. When oxides react with water, they are 'hydrated' (e.g. CO2 + H2O -> H2CO3, Na2O + H2O -> 2NaOH)

so considering the bonds of X-O-H (where X is a main group atom), one that forms when the oxide of X reacts with water.

If X has a high electronegativity, the O-H bond has considerably more ionic character than the X-O bond, so when aqueous, the O-H bond will break first (dissociate), releasing protons in solution.

if X has a low electronegativity (less than that of H), then the X-O bond has more ionic character than the O-H bond, so the X-O bond breaks first, releasing OH- ions in solution.

Thus metal oxides are basic and non-metal oxides are acidic, generally.

 

[KeypadSDM]

Re: Re: dot point blues

Originally posted by spice girl
If X has a high electronegativity, the O-H bond has considerably more ionic character than the X-O bond, so when aqueous, the O-H bond will break first (dissociate), releasing protons in solution.

if X has a low electronegativity (less than that of H), then the X-O bond has more ionic character than the O-H bond, so the X-O bond breaks first, releasing OH- ions in solution.

It's stuff like that they should be teaching in classrooms. About 50 - 60% of the course can be understood simply by logical deductions like the one spice girl made.

 

[fashionista]

typo!!!!!! i meant PROTONS!! not electrons!! sorry!

 

[fashionista]

if such a question arises in the hsc and i use the post--hsc explanation spice girl gave (Thanx sooo much for it!!) will i be marked down?

 

[Ragerunner]

No you won't.

But you must make sure you have written down the stuff they expect you to know. i.e. stuff from the syllabus.

So you can't talk about stuff off the syllabus even though it's correct.

 

[iambored]

Originally posted by fashionista

• Analyse the position of these non-metals (which form acidic oxides) in the periodic table and outline the relationship between the position of elements in the peroiodic table and the acidity/basicity of oxides
  

• 
  i rang the advice line about this one, twice, and they both said we didn't have to know about electronegativities. but it wouldn't hurt to know it!
  
  they told me that we are looking at carbon, nitrogen and sulfur i think it was (look in the syllabus, it says it on the ledt had side.)
  
  you have to remember non metallic character increases from left to right, and from bottom to top.
  
  so the one which was further to the right was least acidic, as it was the least non-metal.
  
  the other two were equal acidity (check out the periodic table, they cancelled each other out)
  
  if i have made a mistake with anything post it because i am rusty on positions and non-metals etc.