How can you calculate the valency of each element ?
The valency is the number of the electrons that an atom gains , loses or even shares during a chemical reaction , The valency is the number of electrons that an atom needs to gain or lose on order to achieve noble gas electronic configuration ,
The chemical reaction , the atoms try to reach the stable state by losing their outermost electrons ( as in case of the metals ) or by sharing a number of electrons with other atoms ( as in case of nonmetals ) .
You should know the valency of the elements or the ions to write the chemical formula of a compound , Chlorine has a valency of 1 as it needs to gain 1 electron to achieve noble gas electronic configuration .
The atoms try to reach the stable state by gaining a number of electrons to complete the outer shell by ( 8 ) electrons ( as in case of nonmetals ) .
The outermost electrons of an atom determine its valency , the valency of an element measures its ability to combine with the other elements , The valency is determined by the number of electrons in the outer shell of each atom of an element .
The valency of some elements in the modern periodic table
The elements in group ( 1 A ) in the modern periodic table have one valent electron in their outer shell , They are very active , they are mono-valent elements as they have only one electron in their outermost energy levels .
The valency of the alkaline earth metals in group ( 2 A ) is divalent , they are divalent elements as they have two electrons in their outermost energy levels .
The elements of group ( 7 A ) are mono-valent elements as their outermost energy levels have ( 7 ) electrons , The elements in group ( 18 ) in the modern periodic table are the noble gases which have a valence of zero as the valence shell is saturated with 8 electrons .
To determine the valency of the ionic molecule phosphorus tetraoxide ( PO4 , four atoms of oxygen and one atom phosphorus ) you should multiply the total valency of the four oxygen atoms ( valency 2 ) and subtract that from the valency of the phosphorus atom ( valency 5 ) , That reveals the valency of ( PO4 ) is 3 .
The valency of an element is always a whole number , and some elements exhibit more than one valency , they have more than one valency such as sulphur ( S ) is divalent , tetravalent and hexavalent .
Nitrogen ( N ) is trivalent and pentavalent while phosphorus ( P ) is trivalent and pentavalent , The valency of copper I is monovalent while the valency of copper II is divalent .
The valency of Iron [II] sulfate or ferrous sulfate is divalent as in FeSO4 , the valency of iron is two while the valency of Iron [III] sulfate or ferric sulfate is trivalent as in Fe2(SO4)3 , the valency of iron is three .