Answer:
Valence electrons or outer electrons are most important as they participate in bonding. The octet rule states that atoms gain, lose, or share valence electrons to have filled energy levels.. this gives atoms a stable configuration like that of the nearest noble gas.
An element is a mixture of two isotopes. One isotope has an atomic mass of 34.969 amu and an abundance of 64.88%. The other isotope has an atomic mass 36.966 amu.
