[immascalymanfish]

Hey, so in grade 9 and 10 we were taught the number of electrons in each shell is 2, 8, 8, 18, etc

Today in grade 11 chemistry our teacher told us about electron configuration, and she told us the 'real' amount of electrons in each shell goes 2, 8, 18, 32, 50, etc.  or 2n^2. 

so whats with this 2, 8, 8, 18 thing then? 

[ATMyller]

They are the octets where the outermoust shell has 8 electrons (full s and p orbitals), 2 for first row because there's only s orbital and 18 for 4th and 5th row because 3d and 4d orbitals (each holding 10 electrons) are filled before 4p and 5p orbitals respectively. For 6th and 7th row it's 32 electrons due to 4f anf 5f orbitals (14 electron each) filling before 5d and 6d orbitals.

In short: the shells are not filled as full shells after 3rd row, but electrons "leak" to higher shells instead.

[Borek]

Hey, so in grade 9 and 10 we were taught the number of electrons in each shell is 2, 8, 8, 18, etc

You were either taught wrong, or you misunderstood, or you remember it wrong. Could be these were not numbers of electrons in the shell, but numbers of valence electrons.