2.1.3.1 octet rule

1. 2.1.32.1.3
Octet RuleOctet Rule

2. The The octet ruleoctet rule is a simple chemical is a simple chemical
rule of thumb rule of thumb
Octet Rule says Octet Rule says atoms with 8 electrons atoms with 8 electrons
in their outer shell are stablein their outer shell are stable
Atoms tend to combine in such a way Atoms tend to combine in such a way
that they each have eight electrons in that they each have eight electrons in
their valence shells, their valence shells, giving them the giving them the
same electron configuration as a noble same electron configuration as a noble
gas.gas.
The nearest Nobel gas The nearest Nobel gas

3. The rule applies to the main-group The rule applies to the main-group
elements, especially carbon, elements, especially carbon,
nitrogen, oxygen, the halogens, and nitrogen, oxygen, the halogens, and
also to metals such as sodium or also to metals such as sodium or
magnesium. magnesium.
In simple terms, molecules or ions In simple terms, molecules or ions
tend to be most stable when the tend to be most stable when the
outermost electron shells of their outermost electron shells of their
constituent atoms contain 8 constituent atoms contain 8
electrons.electrons.

4. Noble GasesNoble Gases
 group of elements were discovered at the end group of elements were discovered at the end
of the 18of the 18
thth
century century
They were un-reactive so they were called the They were un-reactive so they were called the
““Noble GasesNoble Gases””
Later they were called “Later they were called “Inert GasesInert Gases” as they did ” as they did
not react and it sounded more scientific.not react and it sounded more scientific.
Now called “Noble” again because they do Now called “Noble” again because they do
react under extreme conditionsreact under extreme conditions
Atoms with a full outer shell of electrons are Atoms with a full outer shell of electrons are
very stablevery stable

5. LimitationsLimitations
Doesn’t allow for Doesn’t allow for
 H, He or Li H, He or Li
[stable with 2 e[stable with 2 e
- -
in their outer shells] - in their outer shells] -
Duet RuleDuet Rule
 Transition elements - 18 electron ruleTransition elements - 18 electron rule
 BFBF
33 which only has 6 e which only has 6 e
--
in its outer in its outer
shellshell

6. How can atoms get a full outer How can atoms get a full outer
shell?shell?
Give away electronsGive away electrons
Take in electronsTake in electrons
Share electronsShare electrons
Don’t bother getting a full outer Don’t bother getting a full outer
shell at all – (Rare but does shell at all – (Rare but does
happen [BFhappen [BF
33])])

7. How can atoms get a full outer How can atoms get a full outer
shell?shell?
Give away electronsGive away electrons
Take in electronsTake in electrons
Share electronsShare electrons
Don’t bother getting a full outer Don’t bother getting a full outer
shell at all – (Rare but does shell at all – (Rare but does
happen [BFhappen [BF
33])])