Author Topic: Edexcel CHEMISTRY DOUBTS!!!! (Read 254124 times)

mdwael · « **Reply #1035 on:** May 11, 2011, 04:32:25 pm »

Explain why the first ionization energies generally increase across the period
sodium to argon (Na to Ar).

RoRo · « **Reply #1036 on:** May 11, 2011, 04:40:29 pm »

Quote from: mdwael on May 11, 2011, 04:32:25 pm

Explain why the first ionization energies generally increase across the period
sodium to argon (Na to Ar).

As you go across a period,
1. The charge on the nucleus increases, the number of protons in the nucleus increases, so the nucleus becomes more positively charged, so the electrons are attracted more strongly to the nucleus, so more energy would be required to remove an electron and hence the first ionization energy is greater.

2. Due to the increase in the nuclear charge and the stronger attraction, the electrons are closer to the nucleus and hence they are attracted more strongly than the ones further away, so more energy would be required to remove an electron and hence the first ionization energy is greater.

Aadeez || Zafar · « **Reply #1037 on:** May 11, 2011, 05:19:57 pm »

Quote from: mdwael on May 11, 2011, 04:32:25 pm

Explain why the first ionization energies generally increase across the period
sodium to argon (Na to Ar).

see this really helpfull

http://www.khanacademy.org/v/periodic-table-trends--ionization-energy?p=Chemistry

mdwael · « **Reply #1038 on:** May 11, 2011, 05:58:20 pm »

Explain why the first ionization energy of aluminium is less than that of
magnesium

Amelia · « **Reply #1039 on:** May 11, 2011, 06:12:31 pm »

Quote from: mdwael on May 11, 2011, 05:58:20 pm

Explain why the first ionization energy of aluminium is less than that of
magnesium

Compare their electronic configurations

Magnesium : 1s² 2s² 2p⁶ 3s²
Aluminium: 1s² 2s² 2p⁶ 3s² 3p¹

The outer electron in aluminium is in a p sub-level. This is higher in energy than the outer electron in magnesium, which is in an s sub-level, so less energy is needed to remove it.

Aadeez || Zafar · « **Reply #1040 on:** May 11, 2011, 07:35:03 pm »

Quote from: Amelia on May 11, 2011, 06:12:31 pm

Compare their electronic configurations

Magnesium : 1s² 2s² 2p⁶ 3s²
Aluminium: 1s² 2s² 2p⁶ 3s² 3p¹

The outer electron in aluminium is in a p sub-level. This is higher in energy than the outer electron in magnesium, which is in an s sub-level, so less energy is needed to remove it.

ya she is absoleutly right

guMnam · « **Reply #1041 on:** May 13, 2011, 10:30:37 am »

why graphite conducts electricity in only one direction while other metals conduct it in all directions ??

The Golden Girl =D · « **Reply #1042 on:** May 13, 2011, 12:10:40 pm »

Quote from: guMnam on May 13, 2011, 10:30:37 am

why graphite conducts electricity in only one direction while other metals conduct it in all directions ??

I believe it's because it has London forces between the layers and covalent bonding within the layer.

Not sure of the details which is why I didn't mention them.

guMnam · « **Reply #1043 on:** May 13, 2011, 12:20:26 pm »

metalic bonding within the layer :S... macro molecule . stong covalent bonds between carbon atom,.. each atom is bonded wid 3 other carbon atoms..tht means 1 e is free.. tht allows the conduction.... the point is.. y only one direction

Malak · « **Reply #1044 on:** May 13, 2011, 07:34:38 pm »

Quote from: guMnam on May 13, 2011, 12:20:26 pm

metalic bonding within the layer :S... macro molecule . stong covalent bonds between carbon atom,.. each atom is bonded wid 3 other carbon atoms..tht means 1 e is free.. tht allows the conduction.... the point is.. y only one direction

The conductivity in graphite is direction dependent
When talking about In plane (parallel): There is one delocalized electron per carbon within a layer therefore electrons can move easily along layers
They wont conduct electricity in Perpendicular plane: There is an energy gap between the layers ( like one layer which is above and the other below it) which is too large for electron transfer.

So it is in one direction only that is along layers

Malak · « **Reply #1045 on:** May 14, 2011, 02:19:56 pm »

Can anyone explain me briefly
How to balance ionic equations using oxidation number

And specifically i have a problem with this one
IO₄^- + I^- + H⁺ --> I₂ + H2O

Thx

The Golden Girl =D · « **Reply #1046 on:** May 14, 2011, 02:41:24 pm »

Quote from: ang3l on May 14, 2011, 02:19:56 pm

Can anyone explain me briefly
How to balance ionic equations using oxidation number

And specifically i have a problem with this one
IO₄^- + I^- + H⁺ --> I₂ + H2O

Thx

I hope this helps ;

http://www.chemguide.co.uk/inorganic/redox/equations.html

http://www.sparknotes.com/testprep/books/sat2/chemistry/chapter6section3.rhtml

http://www.chemistry.co.nz/chemequa.htm

http://blip.tv/file/3305442

GG

Amelia · « **Reply #1047 on:** May 14, 2011, 04:54:17 pm »

Quote from: ang3l on May 14, 2011, 02:19:56 pm

And specifically i have a problem with this one
IO₄^- + I^- + H⁺ --> I₂ + H2O

Thx

Here
.

Malak · « **Reply #1048 on:** May 14, 2011, 06:22:04 pm »

^^ Thx both

Can anyone state general errors and precautions for acid base titration

thx

EMO123 · « **Reply #1049 on:** May 15, 2011, 07:02:55 am »

Quote from: ang3l on May 14, 2011, 06:22:04 pm

^^ Thx both

Can anyone state general errors and precautions for acid base titration

thx

http://www.khanacademy.org/v/acid-base-titration?p=Chemistry
hope it helps(May be)

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