Valency of elements

 The valency of an element is a measure of its ability to combine or bond with other elements to form compounds. It tells us how many chemical bonds an atom of that element can form when it reacts with other atoms.

Here's a simple breakdown:

1. Valency depends on an element's outermost electron shell. Elements "want" to have a full outer shell of electrons because this makes them stable.

2. Elements in the same column (group) of the periodic table often have similar valencies. For example, elements in Group 1 like hydrogen and sodium have a valency of 1 because they have one electron in their outer shell, which they can easily lose to form a bond.

3. Elements in Group 2 have a valency of 2 because they need to lose two electrons to have a full outer shell.

4. Elements in Group 17 have a valency of 1 because they need to gain one electron to complete their outer shell.

5. Elements can also share electrons to achieve a full outer shell, and their valency reflects how many bonds they can form. For example, oxygen has a valency of 2 because it can share two electrons to fill its outer shell.

So, valency is like a "bonding capacity" that elements have based on their electron configuration, and it helps us predict how they will combine with other elements to create compounds.