They emit radiation. Which can be very harmful to living things, as well as some non living things. I hope i answered you question :)
Fluorine is used to strengthen the enamel of your teeth, it can be used in acid form to etch glass, and chlorine is used in our drinking water and swimming pools. They're all part of the halogen family
The Sun, like most other astronomical objects (planets, asteroids, galaxies, etc.), rotates on its axis. Unlike Earth and other solid objects, the entire Sun doesn't rotate at the same rate. ... The Sun's rotation rate decreases with increasing latitude, so that its rotation rate is slowest near its poles.
Because they have the same number of electrons in the outer shell, they have the same reactivity (they all want to lose/gain a certain amount of electrons to have a full shell of 8), so they have the similar melting, boiling points etc because they all undergo very similar reactions to certain factors so have similar outcomes
