Explanation:

- Linus Pauling was a key figure in chemistry, renowned for his work on the nature of the chemical bond.

- He developed the concept of electronegativity, which is a measure of an atom's ability to attract and hold onto electrons.

- Pauling arbitrarily assigned a value of 4.0 to Fluorine when creating the electronegativity scale to provide a reference point. ??

- This scale helps in predicting the behavior and reactivity of different elements.

- The halogens include Fluorine, Chlorine, Bromine, Iodine, and Astatine.

- Iodine, Astatine, and Bromine don't hold the standard 4.0 electronegativity in this context.