Question

filling of electron starts from ns and completely last filled orbital in periodic table is np orbital.....why...?

Answer 1

coz sbse phle e- ns me jaenge then (n-1) d then 1e- in np then in (n-2)f then rest all in np.... ye to tab h jab atom k pass d or f orbital ho ....otherwise to direct p orbital me jaenge

Answer 2

Because of bohr burry rule says that orbital filling will take place from lower energy orbital to higher energy orbital and s is lower in energy than p aufbau principle also says same