How to find valency of different elements

- How to find valency of elements
- How to find valency of elements above 20
- How to find valency of elements in periodic table
- How to find valency of elements class 9
- How to find valency of transition elements
- How to find valency of all elements
- How to find valency of an element
- How to find valency of higher elements
- How to find valency of 20 elements
- Valency of chemical elements
- How to know valency of elements
- How to find number of valence electrons from electron configuration