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WHAT ARE THEY?Rare earths are a group of 17 elements including 15 silvery-white metals called lanthanides, or lanthanoids, plus scandium and yttrium. ... which reduce combustion engine emissions ...
Trace gases are gases that are present in small amounts within an environment such as a planet's atmosphere.Trace gases in Earth's atmosphere are gases other than nitrogen (78.1%), oxygen (20.9%), and argon (0.934%) which, in combination, make up 99.934% of its atmosphere (not including water vapor).
The rare-earth elements (REE), also called the rare-earth metals or rare earths, and sometimes the lanthanides or lanthanoids (although scandium and yttrium, which do not belong to this series, are usually included as rare earths), [1] are a set of 17 nearly indistinguishable lustrous silvery-white soft heavy metals. Compounds containing rare ...
The troposphere is the lowest layer of Earth's atmosphere. It extends from Earth's surface to an average height of about 12 km (7.5 mi; 39,000 ft), although this altitude varies from about 9 km (5.6 mi; 30,000 ft) at the geographic poles to 17 km (11 mi; 56,000 ft) at the Equator, [17] with some variation due
Atmospheric chemistry is a branch of atmospheric science that studies the chemistry of the Earth's atmosphere and that of other planets. This multidisciplinary approach of research draws on environmental chemistry, physics, meteorology, computer modeling, oceanography, geology and volcanology, climatology and other disciplines to understand both natural and human-induced changes in atmospheric ...
Rare gases is another term that was used, [7] but this is also inaccurate because argon forms a fairly considerable part (0.94% by volume, 1.3% by mass) of the Earth's atmosphere due to decay of radioactive potassium-40. [8] Helium was first detected in the Sun due to its characteristic spectral lines.
At standard temperature and pressure, it forms a monatomic gas with a density of 9.73 kg/m 3, about 8 times the density of the Earth's atmosphere at sea level, 1.217 kg/m 3. [16] It is one of the densest gases at room temperature (a few are denser, e.g. CF 3 (CF 2 ) 2 CF 3 and WF 6 ) and is the densest of the noble gases.
Assuming the growth trend in emissions continues, the CO 2 concentration is on a path to at least double by the latter half of this century. [6] The atmospheric carbon cycle also strongly influences Earth's energy balance through the greenhouse effect, and affects the acidity or alkalinity of the planet's surface