Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table and is a highly reactive nonmetallic element and oxidizing agent that readily forms compounds (notably oxides) with most elements. Photosynthesis releases oxygen, and respiration consumes oxygen.xygen constitutes 49.2% of the Earth's crust by mass and is the major component of the world's oceans (88.8% by mass). Oxygen gas is the second most common component of the Earth's atmosphere, taking up 20.8% of its volume and 23.1% of its mass (some 10 15 tonnes).
The River Liffey (Irish: An Life) is a river in Ireland, which flows through the centre of Dublin.
The Liffey has a lot of tributaries (rivers that flow into it). Its major tributaries include the King's River, River Dodder, the River Poddle and the River Camac. The Liffey does not have any natural lakes, and has only a few islands.There are a few areas with rapids, mostly as the river comes close to Dublin city. There are dams built for three hydroelectric power stations along the river, at Poulaphouca, Golden Falls and Leixlip.he Liffey has a lot of tributaries (rivers that flow into it). Its major tributaries include the King's River, River Dodder, the River Poddle and the River Camac. The Liffey does not have any natural lakes, and has only a few islands.