The most important nutrients and vitamins for healthy hair are:

Protein: Since hair consists of keratin, consuming adequate amount of protein is necessary.
Iron: Oxygen needed by the scalp for hair growth is carried there by iron.
Biotin: Common B vitamin to support strong, healthy hair including biotin.
Vitamin C: Vitamin C supports the production of collagen –a protein imperative to hair structure.
Zinc: Zinc is an essential mineral for healthy hair growing.

Answer for the second question is

Chemical is any substance with a definite composition and specific characteristics. Simple substances are these which may be chemical compounds or alloys.

Chemicals are all around us. They are in the air we breathe, food we take, and water we drink. Those are also used in many products, including medicine, cleaning products and plastic for instance.

There are various ways of classifying chemicals such as, state of matter – solid, liquid or gas; chemical composition and, physical or chemical properties.
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence