Question

Can someone please explain to me how the Octet rule is used?

Answer 1

@Rushwr

Answer 2

The octet rule is a chemical rule of thumb that reflects observation that atoms of main-group elements tend to combine in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas. The rule is especially applicable to carbon, nitrogen, oxygen, and the halogens, but also to metals such as sodium or magnesium.

Answer 3

Chemical rule that states that atoms of low atomic number tend to combine or become ions so that they each have eight electrons in their valence shell, giving them the same electron configuration as a noble gas (and thus more stability).

This is done by bonding either ionically , metallically or covalently. A ionic bond is a bond between a metal and non-metal where it is a give and take relationship. A metallic bond is between metals only where electrons are pooled together. A covalent bond occurs between non-metals only where they share electrons. In doing this they can obey the octet rule losing, gaining or sharing so that they can have an outer shell of eight electrons.
There are some exceptions. A few elements do not need the full 8 valence electrons to be stable (ex. hydrogen, boron, beryllium) and a few can be stable with more than 8 valence electrons (ex. phosphorus and sulfur).

Answer 4

One limitation of the octet rule is that it cannot be applied to the nonmetals after silicon in the Periodic Table.
These elements can “expand their octet” and have more than eight valence electrons around the central atom.
Molecules with an odd number of electrons such as NO and NO2 cannot satisfy the octet rule.One atom must have an odd number of electrons.

Answer 5

Hey I'm sorry.. I know it's a bit confusing but I'll see if I can teach u more tomorrow, cuz now I'm a little busy !!!! Really really sorry that I can't help you right now !

Answer 6

That is okay! I understand being really busy and thanks!

Answer 7

The octet rule is a simple rule that defines maximum no. of valence electrons around atoms and is used extensively for determining Lewis structures. The octet rule is actually quite a lousy rule that works consistently only for C,N,O and F (and H using 2 electrons instead of 8)
For other elements, like S, P etc, they can have expanded valence shells or electron deficient shells (like Be) which don't obey the octet rule.

Let's give an example.
Draw the Lewis structure of water (H2O)
First we identify how many valence electrons we have - this will be (1x2 + 6) = 8 valence electrons.
Now we draw it H - O - H. This implies two bonds (so four electrons in bonding), leaving 2 lone pairs. Where do they go? Well octet rule tells us it is optimal for O to have a total of 8 valence electrons around it. It already has 4 from the 2 bonding pairs, so we add 2 lone pairs to O to make 8.

What about CO2?
Begin with valence electrons: (4+2x6) = 16 valence electrons
Let's start with O - C - O.
This expends 2 pairs of electrons for bonding (4), so we have 12 e's left to place. We can put 6 on both O's to use them up completing the octet rule for O's but that means C has only 4 electrons, violating the octet rule.

Let's try O=C - O. This uses immediately 6 electrons, due to the extra double bond. We have 10 e's left to place. We can try putting 4e's on the double bonded O, and 6 e's on the single bonded O, but the C is left with only 6 valence electrons.
So try O=C=O. This uses up 8 bonding electrons leaving 8 left...which we can split into 2 lots of 4 for each O, and voila, all atoms have 8 valence electrons.
This is the basis of the octet rule.

Answer 8

Thank you all so much @Rushwr @Jonaho and @willowwest17 !!!! ^^ I think I basically understand it now. So the octet rule is mostly used to determine Lewis dot structures?

Answer 9

exactlyyy...(: good luck!

Answer 10

Thanks! :)