Atoms of the same element that have a different number of electrons are called?

The electronic structure or chlorine is 2.8.7 what is the electronic structure of fluorine?

In order of decreasing light-transmitting capabilities of materials, which is the correct sequence? a. transparent -> translucent -> opaque b. opaque -> transparent -> translucent c. opaque -> translucent -> transparent d. translucent -> transparent -> opaque

What is friction? how does it affect the motion of an object?