## Tuesday, 14 September 2010

### DOT AND CROSS DIAGRAM

How do you draw the dot and cross diagrams for:?
Aluminium oxide
Carbon Tetrachloride
andSulfur dioxide?

Aluminium oxide is an ionic compound. So, there is a complete transfer of electrons from aluminium to oxygen atom.

In aluminium oxide ( Al2O3), each atom of Al will transfer three electrons to the oxygen atoms. So, the two Al atoms will transfer a total of six electrons to the three oxygen atoms (each oxygen atom will receive two electrons).

[: Al :]^3+ [ O ]^2-

{All togather there are eight dots around Al and O is surrounded by six cross and two dots. Dots are electrons from Al and crosses are electrons of O}

For carbon tetrachloride, CCl4, Write the C at the centre and is surrounded by four Cl. Between each of the C and Cl is placed a dot and a cross.

Then, six dots around each of the Cl atom.For sulphur dioxide,

SO2, Write the S at the centre and the two O on each side ( in 'V' shaped).
Put two dots and two crosses between S and O.
Then another two dots for S.
Lastly, put four crosses around each O. [ You will fine that there are ten electrons around S.
This is possible because of the expansion of octet]