I II IIIIVVVI VIIVIIIIX X XI XIIXIII XIV XV XVI XVII XVIII XIX XX XXIXXII XXIII XXIV ● Homework
Learning ObjectivesTo understand the trends in properties and reactivity that the group 16 elements: the chalcogens.
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The chalcogens room the first group in the p block to have actually no stable metallic elements. All isotope of polonium (Po), the only metal in team 16, room radioactive, and only one facet in the group, tellurium (Te), can also be defined as a semimetal. Together in teams 14 and also 15, the lightest element of team 16, oxygen, is uncovered in nature as the totally free element.
Of the team 16 elements, just sulfur was recognized in old times; the others were not uncovered until the so late 18th and also 19th centuries. Sulfur is commonly found together yellow crystalline shop of essentially pure S8 in areas of intense volcanic activity or roughly hot springs. As early on as the 15th century BC, sulfur was supplied as a fumigant in Homeric greece because, as soon as burned, the produces SO2 fumes that room toxic to most organisms, consisting of vermin hiding in the walls and under the floors the houses. Therefore references come sulfur are common in ancient literature, commonly in the paper definition of religious purification. In fact, the association of sulfur v the magnificent was therefore pervasive the the prefixes thio- (meaning “sulfur”) and also theo- (meaning “god”) have the exact same root in old Greek. Though used primarily in the manufacturing of sulfuric acid, sulfur is likewise used to manufacture gunpowder and as a cross-linking agent because that rubber, which enables rubber to hold its shape but retain its flexibility.
Group 16 is the very first group in the ns block with no stable metallic elements.
Oxygen to be not uncovered until 1771, as soon as the swedish pharmacist Carl Wilhelm Scheele discovered that heating compounds such as KNO3, Ag2CO3, and also HgO developed a colorless, odorless gas that sustained combustion better than air. The outcomes were not published immediately, however, so Scheele’s job-related remained unknown till 1777. Unfortunately, this was almost two year after a paper by the English starrkingschool.netist Joseph Priestley had actually been published, describing the isolation that the very same gas by utilizing a magnifying glass to focus the sun’s beam on a sample the HgO. Oxygen is used mainly in the stole industry throughout the counter of rudely iron come steel utilizing the Bessemer process. One more important industrial use of oxygen is in the manufacturing of TiO2, i beg your pardon is typically used together a white colors in paints, paper, and plastics.
Tellurium was uncovered accidentally in 1782 through the Austrian starrkingschool.netist Franz Joseph Müller von Reichenstein, the cook surveyor the mines in Transylvania who was also responsible because that the evaluation of ore samples. The silvery-white metal had the same thickness as antimony but very different properties. Because it was challenging to analyze, Müller dubbed it metallum problematicum (meaning “difficult metal”). The surname tellurium (from the Latin tellus, definition “earth”) to be coined by one more Austrian starrkingschool.netist, boy name Klaproth, who demonstrated in 1798 the Müller’s “difficult metal” was in reality a brand-new element. Tellurium is used to shade glass and also ceramics, in the manufacture of blasting caps, and in thermoelectric devices.
Jöns Jakob Berzelius (1779–1848)
Berzelius was born into a well-educated sweden family, however both parents died when he was young. That studied medicine at the university of Uppsala, where his experiments with electroshock therapy led to his interests to revolve to electrostarrkingschool.netistry. Berzelius devised the device of starrkingschool.netical notation that we use today. In addition, he discovered six elements (cerium, thorium, selenium, silicon, titanium, and also zirconium).
Because selenium and tellurium are starrkingschool.netically similar to sulfur, they space usually uncovered as minor contaminants in steel sulfide ores and are generally recovered together by-products. Even so, they room as abundant in Earth’s crust as silver, palladium, and gold. Among the best sources of selenium and tellurium is the “slime” deposited during the electrolytic purification the copper. Both that these aspects are well known for the vile odors of countless of your compounds. For example, as soon as the body absorbs even trace quantities of tellurium, dimethyltellurium <(CH3)2Te> is produced and slowly exit in the breath and also perspiration, leading to an extreme garlic-like smell that is generally called “tellurium breath.”
With their ns2np4 electron configurations, the chalcogens are two electrons short of a fill valence shell. Therefore in reactions through metals, they tend to get two extr electrons to form compounds in the −2 oxidation state. This propensity is biggest for oxygen, the chalcogen v the highest possible electronegativity. The heavier, less electronegative chalcogens can lose either four np electron or four np and two ns electrons to kind compounds in the +4 and +6 oxidation state, respectively, as displayed in Table number \(\PageIndex1\). Similar to the other groups, the lightest member in the group, in this situation oxygen, differs greatly from the others in size, ionization energy, electronegativity, and electron affinity, so its starrkingschool.netistry is unique. Additionally as in the other groups, the second and 3rd members (sulfur and also selenium) have similar properties because of shielding effects. Just polonium is metallic, forming either the sign language Po2+ or Po4+ ion in aqueous solution, relying on conditions.
|atomic massive (amu)||16.00||32.07||78.96||127.60||209|
|atomic radius (pm)||48||88||103||123||135|
|density (g/cm3) at 25°C||1.31 (g/L)||2.07||4.81||6.24||9.20|
|electron affinity (kJ/mol)||−141||−200||−195||−190||−180|
|first ionization energy (kJ/mol)||1314||1000||941||869||812|
|ionic radius (pm)†||140 (−2)||184 (−2), 29 (+6)||198 (−2), 42 (+6)||221 (−2), 56 (+6)||230 (−2), 97 (+4)|
|melting point/boiling allude (°C)||−219/−183||115/445||221/685||450/988||254/962|
|normal oxidation state(s)||−2||+6, +4, −2||+6, +4, −2||+6, +4, −2||+2 (+4)|
|product of reaction v H2||H2O||H2S||H2Se||none||none|
|product of reaction v N2||NO, NO2||none||none||none||none|
|product the reaction with O2||—||SO2||SeO2||TeO2||PoO2|
|product that reaction v X2||O2F2||SF6, S2Cl2, S2Br2||SeF6, SeX4||TeF6, TeX4||PoF4, PoCl2, PoBr2|
|standard palliation potential (E°, V) (E0 → H2E in acidic solution)||+1.23||+0.14||−0.40||−0.79||−1.00|
|type of oxide||—||acidic||acidic||amphoteric||basic|
|valence electron configuration*||2s22p4||3s23p4||4s24p4||5s25p4||6s26p4|
Reactions and also Compounds that Oxygen
As in groups 14 and 15, the lightest group 16 member has the greatest tendency to kind multiple bonds. Hence elemental oxygen is found in nature together a diatomic gas that includes a net double bond: O=O. As with nitrogen, electrostatic repulsion between lone bag of electrons on nearby atoms avoids oxygen from forming stable catenated compounds. In fact, other than for O2, every compounds the contain O–O bonds are perhaps explosive. Ozone, peroxides, and superoxides space all possibly dangerous in pure form. Ozone (O3), one of the most an effective oxidants known, is offered to purify drink water because it walk not create the properties taste connected with chlorinated water. Hydrogen peroxide (H2O2) is for this reason thermodynamically rough that it has actually a propensity to undergo explosive decomposition when impure:
\<2H_2O_2(l) \rightarrow 2H_2O_(l) + O_2(g) \;\;\; ΔG^o = −119\; kJ/mol \label1\>As in teams 14 and 15, the lightest aspect in group 16 has actually the greatest tendency to kind multiple bonds.
Despite the strength of the O=O bond (\(D_\mathrmO_2\) = 494 kJ/mol), \(O_2\) is exceptionally reactive, reacting straight with almost all other elements except the noble gases. Some properties of O2 and related species, such together the peroxide and also superoxide ions, are in Table \(\PageIndex2\). With few exceptions, the starrkingschool.netistry the oxygen is limited to an adverse oxidation states because of that is high electronegativity (χ = 3.4). Uneven the other chalcogens, oxygen walk not form compounds in the +4 or +6 oxidation state. Oxygen is 2nd only come fluorine in its capacity to stabilize high oxidation states of steels in both ionic and also covalent compounds. Because that example, earlier is a stable solid that contains silver in the unexplained Ag(II) state, whereas OsO4 is a volatile heavy that consists of Os(VIII). Because oxygen is therefore electronegative, the O–H shortcut is highly polar, producing a huge bond dipole moment that makes hydrogen bonding much more important because that compounds the oxygen than for comparable compounds that the other chalcogens.
Metal oxides are usually basic, and also nonmetal oxides are acidic, whereas oxides of facets that lie on or near the diagonal tape of semimetals are normally amphoteric. A couple of oxides, such together CO and also PbO2, are neutral and do no react with water, aqueous acid, or aqueous base. Nonmetal oxides are commonly covalent compounds in i m sorry the bonds between oxygen and also the nonmetal are polarized (Eδ+–Oδ−). Consequently, a lone pair of electron on a water molecule can strike the partially positively charged E atom to eventually form an oxoacid. An example is reaction sulfur trioxide through water to kind sulfuric acid:
The oxides the the semimetals and also of aspects such as Al that lie near the metal/nonmetal splitting line room amphoteric, as we expect:
Oxides of metals tend to be basic, oxides that nonmetals have tendency to it is in acidic, and oxides of aspects in or close to the diagonal band of semimetals are usually amphoteric.
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Predict the product(s) of every reaction and write a balanced starrkingschool.netical equation for each reaction.SiO2(s) + H+(aq) → NO(g) + O2(g) → SO3(g) + H2O(l) → H2O2(aq) + I–(aq) →
AnswerSiO2(s) + H+(aq) → no reaction 2NO(g) + O2(g) → 2NO2(g) SO3(g) + H2O(l) → H2SO4(aq) H2O2(aq) + 2I−(aq) → I2(aq) + 2OH−(aq)