How do you know if something has moved?
a. everything moves
b. it moves in relation to the reference point
c. it moves in relation to a bird flying in the sky

Choose all the answers that apply. fluorine (f) has an atomic number of 9 and an atomic weight of 18.99. fluorine has a. 9 protons b. 10 neutrons c. 18 electrons d. an atomic mass of 19 e. at least one isotope