Chem Help - Trends in the Periodic Table (1 Viewer)

[Seven3121]

Hi everyone,
I need help for a chem assessment i have coming up. I need help on the trends in the periodic table going across periods and down groups. I'v found a few but i'm still missing:
electrical conductivity
melting point
boiling point.
Along with the trend i need to know why that trend occurs... I know it seems like i'm asking for alot but i've searched everywhere on the internet and in textbooks but i can't find anything.
Any help would be appreciated. Thanks in advance.

 

[Wooz]

http://www.boredofstudies.org/courses/science/chemistry/1120212602_2003_Chemistry_Notes_*katie*.doc


3rd and 4th pages.

What textbook do u use?

It should be in all the prelim chem textbooks.
It's in context and conquering.

 

[passion89]

For electrical conductivity -
Because metals are on the left and insulators are on the right, electrical conductivity decreases as you go from left to right.

Why does this occur? Metals in the 1st group can conduct electricity and heat the best because they are (obviously) metals. There is delocalisation of electrons and this means electrons can easily pass from one end of the metal to the other, creating current.
Non metals gain electrons and do not have delocalised electrons floating about.

 

[airie]

Electrical conductivity decreases across a period as explained by passion89, and it increases down a group since the electrons are less attracted to the nucleus, therefore free to move around more. (this is also why the atomic radius increases down a group, and decreases across a period)

Across a period, the melting point and boiling point increases to a max. at Group 4, and after that decreases. They decrease down a group for that the bonding is weaker down the group.

 

[gerg tenrab 07]

the melting points and boiling point increase across a period to period to period 4 then decrease because of the type of bonding that occurs. the general trend is metallic bonding to covalent networks to covalent molecular bonding. the bonding between the atoms is stronger in covelent network than both metallic and covalent molecular. the bonding in metallic is stronger than covalent molecular. therefore the trend is moderate melting/boiling point to high melting/boilng point to low melting/boiling points.

hope it helped