How do you calculate number of valence electrons in an neon?
Neon is noble.
The periodic table is your friend.
Where can neon (
Do you see it?
If not, look for Group VIIIA. If you don't understand Roman numerals, that is '8'.
Octet, you ask? Let me ask you something...
How many tentacles does an Octopus have? Eight, right? The prefix Oct- comes from the Latin for eight.
Octet rule? Yes, atoms want to be stable. In order to be stable, they need to either give, lose or share their electrons to fill their valence shell. Those that naturally have eight are known as the noble, or inert gases.
Noble? Have you ever seen a King or a Queen rummaging in the dirt for a penny? No, don't be silly. They'd never stoop to that level. Group VIIIA elements are the same - they don't need to react, because they already have what they need.
It's this need for stability that is the very reason that different elements tend to react with one another in the first place.
Now, here's why you'll never need to ask a question about valence electrons again...
How many valence electrons do elements from Group VIIA have?
How about Group IIIA ?
Are you beginning to see how this works?
Now beware, some groups are a little different! Groups I & II for example only have one or two valence electrons respectively, so it's easier for them to lose their electrons to reach zero than it is for them to gain the seven or six they'd need to reach an octet - so that's exactly what they do.
This is why we often see elements from Group IA reacting with elements from Group VIIA:
Group IA elements need to lose an electron, Group VIIA elements need to gain one.
The periodic table is a really useful tool, so learn how to use it! Hope this helps.