Thirty-six radioisotopes have been characterized, with the heaviest being terbium with atomic mass of
Oganesson There is no rigorous definition of a nonmetal. Broadly, any element lacking a preponderance of metallic properties can be regarded as a nonmetal.
The elements generally classified as nonmetals include one element in group 1 hydrogen ; one in group 14 carbon ; two in group 15 nitrogen and phosphorus ; three in group 16 oxygensulfur and selenium ; most of group 17 fluorinechlorinebromine and iodine ; and all of group 18 with the possible exception of oganesson.
As there is no widely agreed definition of a nonmetal, elements in the periodic table vicinity of where the metals meet the nonmetals are inconsistently classified by different authors. Elements sometimes also classified as nonmetals are the metalloids boron Bsilicon Sigermanium Gearsenic Asantimony Sbtellurium Teand astatine At.
Metals, in contrast, have more homogenous structures and their properties are more easily reconciled. If solid, they have a submetallic appearance with the exception of sulfur and are mostly brittleas opposed to metals, which are lustrousand generally ductile or malleable ; they usually have lower densities than metals; are mostly poorer conductors of heat and electricity ; and tend to have significantly lower melting points and boiling points than those of metals.
Scatter plot of electronegativity values and standard electrode potentials of chemically active nonmetallic elements, showing a rough correlation between the two properties. The higher the standard electrode potential, the greater is the capacity to act as an oxidizing agent.
A broad progression in nonmetallic character is seen, with the metalloids in the lower left, and oxygen and the nonmetallic halogens in the upper right. Trend lines are shown with and without the anomalous hydrogen and nitrogen values. The R2 values show how close each trend line fits its data points.
Values range from 0. Chemically the nonmetals mostly have high ionisation energieshigh electron affinities nitrogen and the noble gases have negative electron affinities and high electronegativity values [n 1] noting that, in general, the higher an element's ionisation energy, electron affinity, and electronegativity, the more nonmetallic that element is.
Complicating the chemistry of the nonmetals is the first row anomaly seen particularly in hydrogen, boroncarbon, nitrogen, oxygen and fluorine; and the alternation effect seen in arsenicselenium and bromine.
Hydrogen is noted for the different ways it forms bonds. It most commonly forms covalent bonds. This subsequently attaches itself to the lone electron pair of an oxygen atom in a water molecule, thereby forming the basis of acid-base chemistry. Ionisation energies and electronegativities among these elements are consequently higher than would otherwise be expected, having regard to periodic trends.
The small atomic radii of carbon, nitrogen, and oxygen facilitates the formation of triple or double bonds. In this sense they can be regarded as the most metallic of nonmetallic elements. Based on shared attributes, the nonmetals can be divided into the two categories of reactive nonmetal, and noble gas.
The metalloids and the two nonmetal categories then span a progression in chemical nature from weakly nonmetallic, to moderately nonmetallic, to strongly nonmetallic oxygen and the four nonmetallic halogensto almost inert. Analogous categories occur among the metals in the form of the weakly metallic the post-transition metalsthe moderately metallic most of the transition metalsthe strongly metallic the alkali metal and alkaline earth metalsand the lanthanides and actinidesand the relatively inert the noble transition metals.
As with categorisation schemes generally, there is some variation and overlapping of properties within and across each category. One or more of the metalloids are sometimes classified as nonmetals.
Among the noble gases, radon is the most metallic and begins to show some cationic behaviour, which is unusual for a nonmetal.Proper usage of the word terbium. Information about terbium in the r-bridal.com dictionary, synonyms and antonyms. English for Beginners Practical English Travel English Telephone English Banking English Accounting English Dictionary.
terbium - a metallic element of the rare earth group; used in lasers; occurs in apatite and monazite and xenotime and ytterbite atomic number 65, Tb metal, metallic element - any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.
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Terbium is a chemical element with symbol Tb and atomic number It is a silvery-white, rare earth metal that is malleable, ductile, and soft enough to be cut with a knife. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with water, evolving hydrogen gas.
In chemistry, a nonmetal (or non-metal) is a chemical element that mostly lacks metallic attributes. Physically, nonmetals tend to have relatively low melting and boiling points, and densities, are mostly brittle if solid, and are usually poor conductors of heat and electricity; chemically, they tend to have relatively high ionization energy, electron affinity, and electronegativity values.