The Periodic Table is arranged according to? the number of electrons that each element has.
the boiling point of the elements.
the reactivity of the elements.
the number of protons each element has.

The number of protons each element has.

Explanation:

The number of protons each element has is also known as the atomic number. Elements are arranged from left to right and top to bottom in order of increasing atomic number. The order generally coincides with increasing atomic mass. The rows are called periods.

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.