Variable Valency

Under different conditions, the atoms of some elements give away or take up different numbers of electrons. In such cases, those elements exhibit more than one valency. This property of elements is called variable valency. Some elements have electrons in the inner shells (besides the outer shell) that can also participate in chemical bonding. This leads to multiple valencies.

Working:

• An atom's valency depends on the electrons in its outermost shell (valence electrons).
• In some cases, an element may lose or share different numbers of these electrons, leading to multiple valencies.
• Depending on the chemical reaction or the environment, an atom might lose or gain varying numbers of electrons.
• For example, in certain reactions, an atom may use only some of its valence electrons, while in others, it may use all available electrons.

For example,

1. Iron (Fe):

+2: When it loses 2 electrons [e.g., in FeCl₂​].

+3: When it loses 3 electrons [e.g., in FeCl₃​].

2. Copper (Cu):

+1: As in Cu₂O [copper(I) oxide].

+2: As in CuO [copper(II) oxide].

3. Tin (Sn):

+2: In SnCl₂​ [tin(II) chloride].

+4: In SnCl₄​ [tin(IV) chloride].