How to calculate the valency of chloride in aluminium chloride if aluminium is 3?
Answers
Valency of aluminium:
The atomic number of Aluminium is 13 ,so its electronic configuration is 2, 8, 3 .It has 3 electrons in outermost shell . The aluminium atom can lose these 3 electrons to form the aluminium ion ,Al³+, having an inert gas electron configuration of 2,8.
Since one atom of aluminium loses 3 (or 3+) electrons to achieve the inert gas electron configuration.
Valency of chlorine:
The atomic number of chlorine is 17 ,so its electronic configuration is 2, 8, 7 . The chlorine atom has 7 electrons in its outermost shell and it needs one electron to achieve the 8 electron configuration. So the chlorine atom gains 1 electron to form chloride Ion Cl- having an inert gas electron arrangement of 2,8,8.
Since one chlorine atom gains 1 electron to achieve the inert gas configuration so the valency of chlorine is 1(or 1-)..
In AlCl3
Al³+ Cl¹-
3+ 1-
On crossing over the valency of aluminium and chloride ions the formula of aluminium chloride becomes AlCl3
Aluminium chloride contains aluminium ions Al³+ and chloride ions Cl-. Now the valency of aluminium ion Al³+ and is 3 and that of chloride ion is 1. So one aluminium ion Al³+ will unite with 3 chloride ions to form AlCl3.