What is meant by principal quantum number?

What is meant by PAR?

What is meant by matrix?

With the increasing principal quantum number, the energy diference between adjacent energy levels in H-atiom,

What is the total number of orbitals associated with the principal quantum number n=3 ?

Total number of e^(-) that can be accommodated in all orbitals having principal quantum number 3 & azimuthal quantum number 0 is :

Given the relation between radius and principal Quantum number of an atom .