periodic table definition Noble Gases definition chemistry

Janssen shared his findings with English astronomer Sir Joseph Lockyer (1836-1920), who had a worldwide reputation for his work in analyzing light waves. Janssen called it 'helium' after the Greek god Helios, or Apollo, whom the ancients associated with the Sun. What Janssen's spectroscope showed was surprising: a yellow line in the spectrum, never seen before, which seemed to indicate the presence of a previously undiscovered element. To aid him in his observations, he used a spectroscope, an instrument for analyzing the spectrum of light emitted by an object. In 1868, a French astronomer named Pierre Janssen (1824-1907) was in India to observe a total solar eclipse. This is significant, because the elements on Earth are the same as those found in space: thus, it is more than just an attempt at sounding poetic when scientists say that humans, as well as the world around them, are made from 'the stuff of stars.' Helium is an unusual element in many respects -not least because it is the only element to have first been identified in the Solar System before it was discovered on Earth. REAL-LIFE APPLICATIONS Isolation of the Noble Gases HELIUM. One of the factors governing the reactivity of an element is its electron configuration, and the electrons of the noble gases are arranged in such a way as to discourage bonding with other elements. Nonetheless, low reactivity -instead of no reactivity, as had formerly been thought -characterizes the rare gases. Fluorine has also been used to form simple compounds with krypton and radon. However, in 1962 English chemist Neil Bartlett (1932-) succeeded in preparing a compound of xenon with platinum and fluorine (XePtF 6), thus overturning the idea that the noble gases were entirely 'inert.' Since that time, numerous compounds of xenon with other elements, most notably oxygen and fluorine, have been developed. Indeed, helium, neon, and argon have not been found to combine with other elements to form compounds. Due to their apparent lack of reactivity, the noble gases -also known as the rare gases -were once known as the inert gases. Rather than reacting to, or bonding with, other elements, the noble gases tend to remain apart -hence the name 'noble,' implying someone or something that is set apart from the crowd, as it were. There is a reason why noble gas atoms tend not to combine: one of the defining characteristics of the noble gas 'family' is their lack of chemical reactivity. (By contrast, atoms of oxygen -another gas, though not among this group -usually combine to form a molecule, O 2.) Low Reactivity They are colorless, odorless, and tasteless, as well as monatomic -meaning that they exist as individual atoms, rather than in molecules. Obviously, all are gases, meaning that they only form liquids or solids at extremely low temperatures -temperatures that, on Earth at least, are usually only achieved in a laboratory. Several characteristics, aside from their placement on the periodic table, define the noble gases. Their atomic numbers are, respectively, 2, 10, 18, 36, 54, and 86. The six noble gases are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Such is the case with Group 8, which is sometimes called Group 18, a collection of non-metals known as the noble gases. The periodic table of elements is ordered by the number of protons in the nucleus of an atom for a given element (the atomic number), yet the chart is also arranged in such a way that elements with similar characteristics are grouped together. Rare though they are, these gases are a part of everyday life, as evidenced by the helium in balloons, the neon in signs -and the harmful radon in some American homes. Also known as the rare gases, they once were called inert gases, because scientists believed them incapable of reacting with other elements. Along the extreme right-hand column of the periodic table of elements is a group known as the noble gases: helium, neon, argon, krypton, xenon, and radon.

Periodic table definition Noble Gases definition chemistry