A <u><em>developer </em></u>is an oxidizing agent that, when mixed with an oxidation hair color, supplies the necessary oxygen gas to develop color molecules and create a change in hair color.
Mostly hair colors are used to dye the gray hairs. Hair colors are mixed with developer which is act as oxidizing agent. The wisely used developer is hydrogen peroxide. The hair color is made of ammonia and oxidative tints.
These tints consist of small precursors of uncolored dye. These combined with hydrogen peroxide and form large tint molecule. These are then diffuse into cortex of hair and can not get off during shampoo.
This is because ionisation energy increases as we move from left to right in a period. Argon presents in the right most column and Argon is a novel gas and has 8 electrons in outermost orbital. So, it is highly stable. I hope I helped! ^-^
