#1
wassup pit.
hoepfullty some of you out there know basic chemistry, because i need help with this question:
I have to explain why electrical conductivity increases and melting point decreases when going down a group.
I know there are some definate intellectuals and this is prelim HSC stuff.
Thanks in advance
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#2
bcuz u touch ur self at nite...lol jk...i have no idea i don't usually pay attention in chemistry
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#4
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#5
Look at valence electrons; as the electrons get further away (higher shells) from the protons and neutrons, they become more volatile. You can probably work out the rest...

Dragonforce? I don't even know what that is. Isn't it that Japanese card game "Dragon Force Z"?
#6
I'm assuming you're talking about electrical conductivity down group-I... Well basically, when going down a group, the distance of the electrons from the positively charged nucleus increases, which means that the overall attraction of the electrons to the nucleus reduces. This makes it easier for electrons to move around on the surface of the mass of the metal (I'm assuming you know a little bit about metallic bonding?). As for melting point, because the electrons are further away, the ionization energy is less than for elements higher up in a group, so less energy is required to melt the substance.

Hope that helped
#7
Quote by unholy_alliance
I'm assuming you're talking about electrical conductivity down group-I... Well basically, when going down a group, the distance of the electrons from the positively charged nucleus increases, which means that the overall attraction of the electrons to the nucleus reduces. This makes it easier for electrons to move around on the surface of the mass of the metal (I'm assuming you know a little bit about metallic bonding?). As for melting point, because the electrons are further away, the ionization energy is less than for elements higher up in a group, so less energy is required to melt the substance.

Hope that helped


The thing about electrical conductivity is mostly true however it is a bit of a simplification, but will do for prelim HSC. When you get to semiconductors and even some metals, quantum mechanics plays a large role in conductivity (see doping). Melting points of substance are based soley on the strength of intermolecular forces, and so would only decrease when going down a group makes the bond stronger. This is not allways the case e.g. NaF will have a lower MP then NaCl. (see electronegativity).


Again most of this is higher level chemistry/quantum physics. But thats is something you will run into throughout HSC chem. Often things taught are simplifications, often not completely correct, of a more complex process.
#8
Quote by romanqwerty
The thing about electrical conductivity is mostly true however it is a bit of a simplification, but will do for prelim HSC. When you get to semiconductors and even some metals, quantum mechanics plays a large role in conductivity (see doping). Melting points of substance are based soley on the strength of intermolecular forces, and so would only decrease when going down a group makes the bond stronger. This is not allways the case e.g. NaF will have a lower MP then NaCl. (see electronegativity).


Again most of this is higher level chemistry/quantum physics. But thats is something you will run into throughout HSC chem. Often things taught are simplifications, often not completely correct, of a more complex process.


Well, I'm studying HL Chemistry right now, so I know most of what you're talking about... not too sure about conductivity (I know that i've mostly been taught a simplified version) but yes, I know that intermolecular forces come into play for melting points. But TS also didn't make it clear whether he was talking about ionic compounds (as u seem to have suggested) so I assumed he was talking about metals. I based the melting point thing on the fact that metals (for example, in group I) would become more unstable moving down the group from Lithium to Francium.
#9
Quote by unholy_alliance
Well, I'm studying HL Chemistry right now, so I know most of what you're talking about... not too sure about conductivity (I know that i've mostly been taught a simplified version) but yes, I know that intermolecular forces come into play for melting points. But TS also didn't make it clear whether he was talking about ionic compounds (as u seem to have suggested) so I assumed he was talking about metals. I based the melting point thing on the fact that metals (for example, in group I) would become more unstable moving down the group from Lithium to Francium.


Ahh yeah that didnt occur to me. TS is probably talking about things in there elemental states. But in that case, the mp of non metals increases as you go down.

Need more question info.