What traits do synthesis and decomposition share?

Both reactions involve the presence of single elements. The difference is that synthesis has single elements on reactant side whereas decomposition has single elements on product side of a chemical equation.

if two electrons have the same n, the same ℓ, and the same ml, then they are in the same orbital. the pauli exclusion principle states that no two identical fermions (a fancy word for electrons and other subatomic particles like electrons) may occupy the same quantum state in an atom simultaneously.