Question

what is the difference between charge and valency?

Answer 1

charge on an atom means the no of electrons it can gain or loose and valency means the combining capacity of an element
for example take  Na
Here Na+1 In this +1 is the charge on the atom
at the same time
in Na
as it belongs to 1st a group its valency is 1.



Valency formula:
for elements of 1st a to 4th a group elements its is equal to its group no
for elements of 5th a to 8th a valency is equal to 8-group no

Answer 2

THE WAY OF CHARGE ON VALENCY IS CALLED CHARGED VALENCY. charge is always related to atoms whereas valency is related to elements and is similar to the number of ion (negative or positive) present on the element. 
VALENCY IS A COMBINING CAPACITY OF AN ELEMENT.