Reactivity trends of halogen:
1) Melting point and boiling points increased down the
group
2) Colour becomes darker.
E.g. Fluorine (pale yellow)
Chlorine (yellowish-green)
Bromine (reddish-brown)
Iodine (purplish-black)
Astatine (black)
3) The reactivity decreases down the group.
Reactivity:
F > Cl > Br > I > At
I think it is the letter A because they both Make sense
Vas happenin
Hope your day is going well
Atoms are referred to basic unit of matter
Hope this helps *smiles*
Answer:
if you mean "measure" you can use many things. from inches to meters. sometimes if they are big they are measured in "stories". but the smaller the unit is. the harder it is and longer it takes to measure it
