Gallium or Boron - they are in the same group but one level lower or higher. Elements in the same group tend to have similar chemical properties.
Mg
Al
boron
Al
Including S such elements are 8, Na,Mg,Al,SI,P,S,Cl and Ar. (3rd period of periodic table)
chlorine
3
Al
boron
Al
Br (Bromine) is a period 4 element in the same group as F.
It's Al. And it is the thirteenth element on the periodic table.
The period of an element is determined by electronic configuration.Period is same as the number of energy levels of the element.
B (boron)
Including S such elements are 8, Na,Mg,Al,SI,P,S,Cl and Ar. (3rd period of periodic table)
chlorine
It's BROMINE. That is the element that is a liquid in the same period as Fe.
chlorine (Cl)