Periodic tableThe periodic table, also known as the periodic table of the elements, arranges the chemical elements into rows ("periods") and columns ("groups"). It is an organizing icon of chemistry and is widely used in physics and other sciences. It is a depiction of the periodic law, which says that when the elements are arranged in order of their atomic numbers an approximate recurrence of their properties is evident. The table is divided into four roughly rectangular areas called blocks.
Great Oxidation EventThe Great Oxidation Event (GOE), also called the Great Oxygenation Event, the Oxygen Catastrophe, the Oxygen Revolution, the Oxygen Crisis, or the Oxygen Holocaust, was a time interval during the Early Earth's Paleoproterozoic era when the Earth's atmosphere and the shallow ocean first experienced a rise in the concentration of oxygen. This began approximately 2.460–2.426 Ga (billion years) ago, during the Siderian period, and ended approximately 2.060 Ga, during the Rhyacian.
BayA bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a gulf, sea, sound, or bight. A cove is a small, circular bay with a narrow entrance. A fjord is an elongated bay formed by glacial action. A bay can be the estuary of a river, such as the Chesapeake Bay, an estuary of the Susquehanna River. Bays may also be nested within each other; for example, James Bay is an arm of Hudson Bay in northeastern Canada.
