The columns of the periodic table, also referred to as "groups" contain elements with similar reactive properties, due to these elements having a similar configuration of electrons in their outer shell.
<span>The correct answer is d. The reaction releases more energy than it absorbs. An example of an exothermic reaction is fire. Connecting the carbon atoms in wood with the oxygen in the air causes flames and gives of heat and light.</span>
1 mol of Br = 79.9 g
15.7 g / 79.9 g = 0.196 moles of atoms