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.
River Dargle. The River Dargle (Irish: An Deargail, meaning little red spot, so called with reference to the prevailing tint of its rocks) rises in the Wicklow Mountains of Ireland on the northern slopes of Djouce Mountain and flows over the highest waterfall in Ireland, falling 121m (398 feet) at Powerscourt Waterfall.