Simplify the following text for a Grade 8 native English-speaking person.
Original: In a noble gas , an atom tends to have 8 electrons in its outer shell ( except helium , which is only able to fill its shell with 2 electrons ) .
Simplified: These elements would have some electrons in their 5g subshell and thus have more than 32 electrons in the O shell ( fifth principal shell ) . The valence shell is the outermost shell of an atom .