Bromine atoms usually end up with SEVEN valence electrons.
Bromine belongs to group 17 i.e. halogen group. Its atomic number is 35. The electron configuration of Bromine is 1s² 2s²2p⁶ 3s²3p⁶ 4s²3d¹⁰4p⁵. In the last shell, we see 4s²4p⁵, thus 2+5 = 7 valence electrons are present.
The amount of the solute is constant during dilution. So the mole number of HCl is 2*1.5=3 mole. The volume of HCl stock is 3/12=0.25 L. So using 0.25 L stock solution and dilute to 2.0 L.
