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 Callan River joins the Blackwater 1.6 km upstream. Further on, at a bend on the east bank, is the entrance to the first lock of the Ulster Canal. Just upstream, Charlemont Bridge joins the town of Charlemont on the east bank and Moy on the west. The Blackwater's length is 91.3 km (56.75ml).f the Blackwater's flow is measured through its path through the 30 km (19ml) Lough Neagh and onwards to the sea via the 64.4 km (40ml) Lower Bann, the total length is 186.3 km (115.75ml).