|
|
Post by chooijingyew on Mar 20, 2009 8:14:19 GMT -5
Noble gases cannot form bonds with other elements because they have a full valence shell of electrons.
Xenon, which is one of the noble gases, can form the following compounds: xenon difluoride (XeF2), xenon tetrafluoride (XeF4), xenon hexafluoride (XeF6), xenon tetroxide (XeO4), and sodium perxenate (Na4XeO6).
|
|
|
|
Post by Mr Kwok on Mar 20, 2009 8:17:39 GMT -5
Ice is less dense than water because when water freezes, water molecules form hydrogen bonds with each other to form a crystal lattice. In liquid water each molecule is hydrogen bonded to approximately 3.4 other water molecules. In ice each each molecule is hydrogen bonded to 4 other molecules. The ice structure takes up more volume than the liquid water molecules, hence ice is less dense than liquid water.lol. Hi Wen Han, Would you like to explain why is there an expansion? I believe when you learn about solid, liquid and gases, the particles are closest together in solid and furthest apart in gas state. So howcome water is not following this pattern? Regards Mr Kwok  |
|
|
|
Post by elizabeth on Mar 21, 2009 4:57:02 GMT -5
Most ionic compounds are soluble in water but insoluble in organic solvents. This is because the ions attract the water molecules, which disrupts the crystal structure, causing the ions to separate. The ions do not attract molecule of organic solvents and so the solid does not dissolve. ;D ;D ;D
|
|
lum76
New Member
Posts: 3
|
Post by lum76 on Mar 24, 2009 0:13:18 GMT -5
thanks mr kwok
|
|
|
|
Post by brandon on Mar 24, 2009 9:00:54 GMT -5
I guess i shouldnt help Wen Han answer?
Haha.
Anyway,
Bonds in an element would affect the hardness of the object, hence its place on the Moh's Scale.
Such as alkali metals have only one valence electron and larger atomic kernels, which makes the metallic bonds weak. Consequently these metals are soft metals. On the other hand, Diamond is the hardest material on the planet as they have strong intermolecular covalent bonds between its carbon atoms.
|
|
|
|
Post by Mr Kwok on Mar 25, 2009 9:06:06 GMT -5
I guess i shouldnt help Wen Han answer? Haha. Anyway, Bonds in an element would affect the hardness of the object, hence its place on the Moh's Scale.
Such as alkali metals have only one valence electron and larger atomic kernels, which makes the metallic bonds weak. Consequently these metals are soft metals. On the other hand, Diamond is the hardest material on the planet as they have strong intermolecular covalent bonds between its carbon atoms.Hi Brandon, Bonds in an element would affect the hardness of the object? Moh's scale? I am not sure how is it relevant to Wen Han's answer or is it your contribution? Well I have two inputs. Could explain what kernel is (or are?) I don't remember using it in chemistry. Secondly, there is no intermolecular covalent bonds between carbon atoms in diamond. It is intra molecular covalent bond. Diamond is a marcomolecule and within this molecule there is carbon-carbon single bond. Hence, it is intramolecular covalent bond. =) Thanks for your contribution. Now, I eagerly await your reply. =P Regards Mr Kwok |
|
|
|
Post by brandon on Mar 26, 2009 9:49:14 GMT -5
I meant for what i typed as my own input, just that i understood the reason for the statement WenHan made. I'll let him explain himself.
As for kernels, i have honestly no idea as i took that statement from a website.
However, rephrasing that statement, metals are hard depending on the strength of metallic bonds. Thus the smaller the period / group of the metal, the harder the metal, as the forces of attraction between the electrons and nuclei is stronger.
Hence, with this statement, Na > K in terms of hardness. (However, they are often too reactive to conduct such experiments with)
On the otherhand, my other statement would thus prove to be a misconception.
Diamond is the hardest material on the planet as they have strong intermolecular covalent bonds between its carbon atoms.
It was my misconception to state inter molecular bonds, and it is actually in fact intra molecular bonds between one carbon atom and4 other carbon atoms in a tetrahedrel arrangement
|
|
|
|
Post by chooijingyew on Mar 28, 2009 7:04:27 GMT -5
I guess i shouldnt help Wen Han answer? Haha. Anyway, Bonds in an element would affect the hardness of the object, hence its place on the Moh's Scale.
Such as alkali metals have only one valence electron and larger atomic kernels, which makes the metallic bonds weak. Consequently these metals are soft metals. On the other hand, Diamond is the hardest material on the planet as they have strong intermolecular covalent bonds between its carbon atoms.Just my two cents' worth on Brandon's entry: I think atomic kernels are atomic nuclei. As the nuclei gets bigger (means there are more protons and neutrons), the number of electrons would increase as number of electrons = number of protons in an atom and hence the number of electron shells would also increase. With more electron shells, the delocalised electrons in metallic bonding would be further away from the positively charged metal nuclei, resulting in weaker forces of attraction between the metal nuclei and the electrons, in other words, a weaker metallic bond. By this definition atomic kernels could also be atomic shells, but the dictionary definition of 'kernel' is : a small mass around which other matter is concreted; a nucleus; a concretion or hard lump in the flesh. Which means that kernels here are probably nuclei. |
|
|
|
Post by whyeow on Mar 29, 2009 11:01:05 GMT -5
Hi Wen Han, Would you like to explain why is there an expansion? I believe when you learn about solid, liquid and gases, the particles are closest together in solid and furthest apart in gas state. So howcome water is not following this pattern? Regards Mr Kwok The expansion of water on freezing is due to the geometry of the water molecule. Hydrogen bonds forming between the water molecules line up molecules less efficiently (in terms of volume) when water is frozen. |
|
grace
Junior Member
Posts: 82
|
Post by grace on Aug 23, 2013 10:37:29 GMT -5
|
|
grace
Junior Member
Posts: 82
|
Post by grace on Sept 6, 2013 13:48:10 GMT -5
|
|
