Sodium and aluiminium have atomic numbers 11 and 13 respectively. They are sepearated by oneelement in the perodic table, and have valencies of one and three respectively. Chlorine and potassium are also separated by one element in the periodic table with atomic numbers 17 and 19 respecteively

and yet both have the valencies of one. Explain the difference.



This ia because elements chlorine require one electron to gain the nearest noble gas configuration and pottassium needs to loose one electron to gain the nearest inert gas configuration.