Flourine (F), chlorine (Cl), bromine (Br), and iodine (I) are all well-known halogens. These halogens are all on the seventh column of the periodic table. Why are these halogens apart of the same group?
1.They have the same number of atomic orbitals.
2.They have seven electrons in the outer shell.
3.They have the same atomic number.
4.They are the same size.