# Generally, what does a complete valance shell hold?

##### 1 Answer
Mar 29, 2017

Generally, we don't know how many "valance" electrons, unless we know what period we're talking about...

• Period 1 has access to only the $1 s$ orbital at the moment, e.g. two valence electrons max.
• Period 2 has access up to the $2 s$ and $2 p$ orbitals at the moment, e.g. 2 + 6 = ? valence electrons max.
• Period 3 feels free to ignore the so-called "octet rule" when it comes to phosphorus, sulfur, and chlorine. They arbitrarily include the $3 d$ orbitals when they need to, and thus have $18$ valence electrons max. Otherwise, period 3 has the same max as period 2...
• Periods 4 and 5 have the same max as period 2, EXCEPT for the transition metals, which have a max of $18$ (why?).
• Periods 6 and 7 are stated by the periodic table to include the $f$-block, i.e. the max number of valence electrons has increased again to $32$ (how many $f$ orbitals are there for a given $n$?).

Thus, the VERY general and NOT AT ALL ABSOLUTE pattern is $2 , 8 , 8 , 18 , 18 , 32 , 32$.