Modern EraThe modern era is the period of human history that succeeds the Middle Ages (which ended around 1500 AD) up to the present. This terminology is a historical periodization that is applied primarily to European and Western history. The modern era can be further divided as follows: The early modern period lasted from c. AD 1500 to 1800 and resulted in wide-ranging intellectual, political and economic change.
Chemical reactionsA chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur.
