lboogy

Hi, thanks for that, I read it before I posted on here, but now I've read it again and it sinks in!

Hi everyone, Can someone please help me with the above. I don't get why ammonium is positive - I mean, it has an extra H, it hasn't lost an electron. The extra electron gained from the 4th N-H bond would give it an extra electron to NH3, which should give it a negative charge? Also, how/why can it form that 4th N-H bond that takes it from NH3 with a full energy field to NH4? I'm really confused, this is questioning my basic understanding! thanks in advance everyone Gav

thanks for that John, it explainms it very clearly.

Hello everyone, Please could someone explain something for me? When thiosulphate is oxidised, for example, in the following reaction: I2 + (2S2O3)2- -> 2I- + (S4O6)2- I know the 2 electrons have now gone to the 2 iodine atoms, but what are the individual charges of the atoms in the thiosulphate at product stage? thanks in advance Gav the only reason I ask is because in working it out, at product stage we have (2S2O3)1- + 1e-. As oxygen is 2- each, totaling 6-, and the total charge is 1-, I figured the S would have to total 5-, but that would entail one being 3+ and the other being 2+. I only thought sulphur could be 6+, 4+, 0 or 2-.

Hi everyone, I'm struggling to know how to realise how many atoms are in a compound if you are provided with the word of the chemical. For example, for Silver Nitrate I know this is a combination of Ag, N & O. I know the electronic config of Ag is 4f1. I would use this as a basis to work out how many O & N atoms I need to fill the 4th shell of Ag. So Ag needs 13 electrons from O & N. Because N & O are bonded together - does this have a different implication for sharing electrons? Or is this totally wrong and in fact it is ionic bonding? I know when s block & p block bond together they do so through ionic bonding, and 2 p block atoms bond together via covalent bonding - but what about d block atoms with either s or p block atoms? I know the answer is AgNO3 - but I want to know how to get there! If I didn't know that was the answer I would have used as many N & O atoms to fill up the outershell of Ag, but obviously knowing the answer I know this is wrong! thanks for your help Gav

Zule, thanks for explaining. When I said “the flow of electrons that the body somehow manages to break down” I appreciate I didn't write it the best way. I meant electrons detached from the atoms, but I haven't studied physics since GCSE so maybe I got that wrong too, but I understood electron charge to be a flow of electrons detached from atoms.....correct me if I'm wrong!

Hi everyone, I'd be really grateful if anyone could answer this....I was assuming that it was the flow of electrons that the body somehow manages to break down (as in a flow of electrons being a electrical charge). My lecturer didn't seem to know, my text books don't go into it, and neither does wikipedia etc....does anybody know? thanks in advance! Gav

Hi, thanks for both of the above posts, but my question was more just a general one using a specific example. I am wondering, if I have an equation, how can I tell just by looking at the equation which ions are used in the reaction and which ones aren't? Are there any principles to follow?

Hi everyone, I was wondering if you could help me. I am looking at ionic equations, and I'm a little confused. I'm confused about knowing which ions why can omit from the equation. For example: (step 1)HCl(aq)+ NAOH(aq)→NaCl(aq)+H20(l) ions present: (step 2)H+(aq) Cl-(aq) Na+(aq) OH-(aq) → H20(l) Na+(aq) Cl-(aq) So Cl-(aq) & Na+(aq) appear on both sides of the equation and so are spectator ions & can therefore be left out of the equation making the ionic equation: (step 3)H+(aq) OH-(aq) → H20(l) However, what are tghe principles that can be applied to different ionic equations to understand what ions are spectator ions? When deciding what ions are present, how do we know that we should break NaCl down into Cl-(aq) & Na+(aq) but not break H20 down? In step 1, the symbols Na & Cl are together thus NaCl implying to me that they have become 1 molecule & so have reacted. How do we know, by looking at the equation, that they haven't? I hope I've expressed my questions clearly! thanks in advance Gav

John and Fred, once again thanks very much, I think I was just obscuring something that is simple!!!!

Hi John Cuthber & Fred56, First of all thanks for your help. I think Fred56 has explained what I asked, but I'd really like to get a good understanding of these diagrammes...here is a link of what I mean: http://www.ncbi.nlm.nih.gov/books/bv.fcgi?indexed=google&rid=mcb.figgrp.278 I guess what I'm trying to understand is say, when there is an O for oxygen. When a line goes off this O to another point in the hexagon which then has another line going to OH, does this mean that the O is covalently bonded to the other OH? Are all the atoms conected via lines covalently bonded? Also if the OH is also connected to another H there will that initial O be able to covalently bond with the OH as the OH will have all the outer shells full and therefore there wont be any need for that OH to chemically bond with other atoms? Sorry in advance! I guess these are basic questions. I'd really like some website or book detailing them. I never came accross them at GCSe and all of a sudden they are present in A level, without no explanation! sorry! i think they're known as structural formula's rather than chemical diagrammes.

Sorry, I should have been clearer. A Level biology (16-18 yrs), pre uni. I mean the biological molecules for things like gluscose for example. I have a couple of text books, but they just jump in and show one without explaining it....this was never part of the GCSE so it is a jump.... In particular, these are the things I don't understand: a) does a line between 2 atoms mean it is chemically bonded? What signifies what type of bond it is? Are the covalent or ionic bonds? b) When there is a line coming off the top right hand corner of the diagramme with a formula written down, is that the formula of the whole diagramme, or just the formula of another part of the molecule that isn't being drawn (I'm inclined to think the latter as the formula seems to actually be attached to the diagramme rather than as a title for the whole thing). thanks guys!

Hi everyone, I've had a look on the net before asking but couldn't really find anything. I'm looking for some sites that explain chemical diagrammes...I don't expect anyone to explain it just some good sites would be great. I'm not clear about the lines between the letters and also we some parts of the formula are drawn while other parts are written etc etc Any links would be really appreciated!

Hi everyone, I've just got a quick question which I hope people don't mind me asking! Regarding atoms that have a stronger bond between the protons and the electrons the bigger the atomic number is - can anyone tell me why? I would have assumed that due to the fact that while there may be more atoms giving it a higher charge, an atom with a higher atomic number will also have more electrons to bond with and therefore it's increased charge due to it's high atomic umber will be used up on more electrons, than an atom with a smaller atomic number which while it does have a smaller charge, also has fewer electrons to bond with. Can anyone help? thanks in advance!

The example of the OH in brackets that I read was Ca(OH)2(s) - it's calcium hydroxide, but was wondering why the OH are in brackets and without a negative sign?

Hi everyone, sorry for keep posting on here to ask questions, right now though if i come accross something i don't understand this is my best resource - i hope you all don't mind. If you have a formula, say CaCO3 (just for example, my question isn't specific to this formula, it's a more hypothetical one) how can you tell how these elements have bonded? Is it covalent or ionic? Also, I've seen H2O written with (l) after it denoting it is in liquid form. But then in the same formula I've seen other elements written with the (aq) to denote disolved in water. If something is written with the (aq) after it, but H2O is not part of the formula, does it mean that the hydrogen and oxygen from the water is not having an effect in the equation? Also....what does (OH) mean after an element? I know OH- means it's an alkali, but what about when there is no negative sign there? thanks in advance!

ahhh ok - i get it now thanks.

Hi everyone, I'm just wondering about ionic bonding, for eg aluminium oxide. Oxygen has 4 electrons on the outer shell whereas aluminium has 3. So the oxygen atom could gain 2 from aluminium to fill their outer shell, but aluminium would still have one electron on it's outer shell. So what would happen to this? Would it remain with the aluminium? ta!

thanks very much for the help...understood!

Hi everyone, I've just got a few simple questions regarding covalent & ionic bonding....I hope you don't mind! re: ionic bonding. I've read that if sodium metal (therefore neutral sodium atoms) reacts with water, it will result in sodium + ions by getting rid of it's electron on the outside shell. But where would that electron go? The hydrogen and oxygen are already convalently bonded so they have no need to acquire that extra electron to fill up their outer shells. Or would the sodium stimulate the oxygen and hydrogen to break up and create new molecules from sodium, oxygen & hydrogen? re: covalent bonding. If graphite is composed of carbon atoms having 3 covalent bonds - this will not be enough to fill the outside shell so what is the point? If carbon has 4 electrons on it's outer shell, it needs another 4 to fill it. So it already has 4 on the outside shell, it gains 3 more from forming covalent bonds with other carbon atoms. That makes 7, but it needs 8 so there is 1 short. I've read that there are free electrons in graphite. Where do these come from? It appears that there is not enough! thanks for your help in advance

thanks CharonY - understood now.

Hi everyone, I was hoping someone could explain something I was reading? Below is the text I read and I have put my question in bold. Before meiosis begins, the chromosomes are copied exactly. The DNA of each chromosome is replicated to form two chromatids. They then arrange themselves into homologous pairs (both coding for the same characteristics), and prepare for cell division. At this point maternal and paternal chromatids can exchange bits of DNA to recombine their genetic material and increase the potential for variation (If the chromosomes are copied exactly, why would they exhange bits of DNA as the are just swaping like for like? Also if this is before meiosis how can there be both maternal and parental chromatids? Surely this can only happen when the sperm and egg meet?). thanks so much in advance Gav

Hi everyone, I've come accross this on the bitesize revision pages and it doesn't make sense to me, I was hoping someone would be able to explain it, the link is : http://www.bbc.co.uk/school... my problem with is is that the formula for working out the relationship between the voltages on a transformer and the number of turns on a coil is that they seem to change the formula round. First of all it is: Vp/Vs = Np/Ns then they write it as: Vs/Vp = Ns/Np which obviously isn't the same thing unless I'm missing something! They then add in a multiplication when there isn't even one in the formula!!! This is what the question is: "A transformer has 20 turns on the primary and 400 on the secondary. What is the output voltage if the input voltage is 500V?" So following the first formula, I would have thought that this would be: 500/Vs = 20/400, but they do: Vs/Vp = Ns/Np Vs/500 = 400/20 Vs = 500 x (400/20) Vs= 10,000 Volts I don't understand that if the formula is Vp/Vs=Np/Ns they can then turn it around completely to Vs/Vp=Ns/Np, and I also don't understnad how they can put a multiplied by 500 in as there is no multiplication in the original formula. Could anyone shed any light on this for me? I hope someone can help!!!!

thanks Spyman, I understand it now.

Hi everyone, I'd be really appreciative if someone could clarify a few things for me. 1) If voltage is the potential difference, surely the 'difference' necessitates at least 2 different values, so there is something to differ. So, is the voltage the potential difference from one end of a circuit to the other? 2) Is the energy actually from the voltage? Or is it caused (transfered) when the voltage causes the charge to move through the circuit? thanks