The total number of lone electron pairs in BrO2 drawn with two single bonds is​

c- cold periods in earth's history during which glaciers covered much of the surface.

explanation:

16

explanation:

the marks go by 4s

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.