March 28, 2024, 10:11:27 AM
Forum Rules: Read This Before Posting


Topic: Periodic table  (Read 6754 times)

0 Members and 1 Guest are viewing this topic.

Offline iyc

  • Regular Member
  • ***
  • Posts: 24
  • Mole Snacks: +0/-3
  • Gender: Male
  • I'm a llama!
Periodic table
« on: January 17, 2005, 08:20:52 AM »
Down the periodic table, why does the melting point decrease down the Group I?

Offline jdurg

  • Banninator
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1366
  • Mole Snacks: +106/-23
  • Gender: Male
  • I am NOT a freak.
Re:Periodic table
« Reply #1 on: January 17, 2005, 11:23:13 AM »
Well, why do you think it decreases?  Based upon the properties of the elements, you should be able to figure that out.   ;D
"A real fart is beefy, has a density greater than or equal to the air surrounding it, consists

pizza1512

  • Guest
Re:Periodic table
« Reply #2 on: January 18, 2005, 08:21:01 AM »
Look at the table and check out their physical properties!...

 ::)

Offline Donaldson Tan

  • Editor, New Asia Republic
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 3177
  • Mole Snacks: +261/-13
  • Gender: Male
    • New Asia Republic
Re:Periodic table
« Reply #3 on: January 21, 2005, 10:25:26 PM »
group 1 elements are metals, therefore their melting point is dependent on the bond strength of irs metallic structure, which is essentially the attraction of the delocalised electrons and the cations (held in the lattice arrangement). attraction for the delocalised electrons decreases due to increased shielding effect of the valence shell on the nuclear charge of each cation.
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

pizza1512

  • Guest
Re:Periodic table
« Reply #4 on: January 26, 2005, 08:59:09 AM »
It all depends on their atomic masses...


 ::)

Siddharth

  • Guest
Re:Periodic table
« Reply #5 on: January 31, 2005, 11:12:20 PM »
Down the group 1 the size of the elements increases due to which the melting point of elements decreases.

Offline jdurg

  • Banninator
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1366
  • Mole Snacks: +106/-23
  • Gender: Male
  • I am NOT a freak.
Re:Periodic table
« Reply #6 on: February 01, 2005, 09:51:12 AM »
Element size does not alone determine the melting point of the element.  Look at Xenon.  It's radius is about 105 pm, yet it's melting point is FAAAAAAAAAAAAAAAAAR below that of Cesium.  Cesium has a radius of about 300 pm and is a mighty big element, but that is not why its melting point is so low.  (Also, many of the gases and liquids at room temperature have low atomic radii, yet elements which are bigger than them can have much higher melting points).

The real reason why the melting points decrease down Group 1 is due to a combination of electron configuration and element size.  The elements down towards the bottom of group one have a great deal of nuclear shielding going on.  As a result, the electrons are more spaced out due to their own repulsion.  Those outer electrons have a hard time seeing their own nucleus, let alone the nucleus of a surrounding atom.  As a result, the bonding between the atoms is fairly weak which results in a lower melting point.  Elements like lithium and sodium have a higher melting point because their atoms can still see a part of their nuclei so there's a slightly stronger attraction.  Now at this point you might be saying 'yeah, that's exactly what I said before.  The bigger elements have a lower melting point'.  The funny thing is, if you look at the halogens the complete opposite is true.  As you go down the column, the atom sizes increase yet the melting points increase as well.  So saying that one element will melt at a lower temperature than another simply because the atomic radius is bigger is not correct.
"A real fart is beefy, has a density greater than or equal to the air surrounding it, consists

pizza1512

  • Guest
Re:Periodic table
« Reply #7 on: February 03, 2005, 08:44:53 AM »
That's why they're aranged in groups!...


 :P

Sponsored Links