What is the classification for this reaction? so3 (g) + h2o (l) → h2so4 (aq)?

The given reaction is the combination reaction.

There are 6 different types of reaction namely, Combination , Decomposition , Single Displacement , Double Displacement , Combustion, and  Redox reactions.

The reaction given is :

In this reaction by the combination of two reactants, there is the formation of a single product. This type of reaction is the combination reaction. Thus, the given reaction is the combination reaction.

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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.

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.