Which pair of elements will have a similar valence shell electron configuration?

Here we have to determine the pair of elements which have similar valence shell electron configuration.

The nitrogen (N) and phosphorous (P) has same number of electrons (5) in their valence shell, the electronic configuration is ns²np³.

There are number of elements which have the same number of valence electrons. The valence shell electronic configurations are also same but the principal quantum numbers are different.

In the periodic table in a particular group the number of valence electrons and configurations are same. Like-

H, Li, Na, K, Rb, Cs, Fr have the general valence shell configuration i.e. ns¹. (where n = principal quantum number)

The halogen series F, Cl, Br, I, At has the general electronic configuration is ns²np⁵.

Nitrogen & Phosphorus

whats the meaning of /

"the periodic table is arranged in order of atomic number."