first ionization energy (kJ/mol) 1087 787 762 709 716 most common oxidation state +4 +4 +4 +4 +4 ionic radius (pm)† ≈29 ≈40 53 69 77.5 electron affinity (kJ/mol) −122 −134 −119 −107 −35 electronegativity 2.6 1.9 2.0 2.0 1.8 standard reduction potential (E°, V) (for EO2 → E in acidic solution) 0.21 −0.86 −0.18 −0.12 0.79 product of reaction with O2 CO2, CO SiO2 GeO2 SnO2 PbO type of oxide acidic (CO2) acidic neutral (CO) amphoteric amphoteric amphoteric product of reaction with N2 none Si3N4 none Sn3N4 none product of reaction with X2‡ CX4 SiX4 GeX4 SnX4 PbX2 product of reaction with H2 CH4 none none none none *The configuration shown does not include filled d and f subshells. †The values cited are for six-coordinate +4 ions in the most common oxidation state, except for C4+ and Si4+, for which values for the four-coordinate ion are estimated. ‡X is Cl, Br, or I. Reaction with F2 the tetrafluorides (EF4) for all group 14 elements, where E represents any 14 element. Selected Properties of the Group 14 Elements
melting point/boiling point (°C) −210/−196 44.15/281c 817 (at 3.70 MPa)/603 (sublimes)† 631/1587 271/1564 density (g/cm3) at 25°C 1.15 (g/L) 1.82† 5.75‡ 6.68 9.79 atomic radius (pm) 56 98 114 133 143 first ionization energy (kJ/mol) 1402 1012 945 831 703 common oxidation state(s) −3 to +5 +5, +3, −3 +5, +3 +5, +3 +3 ionic radius (pm)§ 146 (−3), 16 (+3) 212 (−3), 44 (+3) 58 (+3) 76 (+3), 60 (+5) 103 (+3) electron affinity (kJ/mol) 0 −72 −78 −101 −91 electronegativity 3.0 2.2 2.2 2.1 1.9 standard reduction potential (E°, V) (EV → EIII in acidic solution)|| +0.93 −0.28 +0.56 +0.65 — product of reaction with O2 NO2, NO P4O6, P4O10 As4O6 Sb2O5 Bi2O3 type of oxide acidic (NO2), neutral (NO, N2O) acidic acidic amphoteric basic product of reaction with N2 — none none none none product of reaction with X2 none PX3, PX5 AsF5, AsX3 SbF5, SbCl5, SbBr3, SbI3 BiF5, BiX3 product of reaction with H2 none none none none none
Property Oxygen Sulfur Selenium Tellurium Polonium atomic symbol O S Se Te Po atomic number 8 16 34 52 84 atomic mass (amu) 16.00 32.07 78.96 127.60 209 valence electron configuration* 2s22p4 3s23p4 4s24p4 5s25p4 6s26p4 melting point/boiling point (°C) −219/−183 115/445 221/685 450/988 254/962 density (g/cm3) at 25°C 1.31 (g/L) 2.07 4.81 6.24 9.20 atomic radius (pm) 48 88 103 123 135 first ionization energy (kJ/mol) 1314 1000 941 869 812 normal oxidation state(s) −2 +6, +4, −2 +6, +4, −2 +6, +4, −2 +2 (+4) radius (pm)† 140 (−2) 184 (−2), 29 (+6) 198 (−2), 42 (+6) 221 (−2), 56 (+6) 230 (−2), 97 (+4) electron affinity (kJ/mol) −141 −200 −195 −190 −180 electronegativity 3.4 2.6 2.6 2.1 2.0 standard reduction potential (E°, V) (E0 → H2E in acidic solution) +1.23 +0.14 −0.40 −0.79 −1.00 product of reaction with O2 — SO2 SeO2 TeO2 PoO2 type of oxide — acidic acidic amphoteric basic product of reaction with N2 NO, NO2 none none none none
Figure: The Synthesis of the First Chemical Compound of Xenon: (a) An apparatus containing platinum hexafluoride, the red vapor at the bottom left, and xenon, the colorless gas in the small tube at the upper right. (b) When the glass seal separating the two gases is broken and the gases are allowed to mix, a bright yellow solid is formed, which is best described as XeF+PtF5−. Subsequent work showed that xenon reacts directly with fluorine under relatively mild conditions to give XeF2, XeF4, or XeF6, depending on conditions; one such reaction is as follows: The ionization energies of helium, neon, and argon are so high (Table above) that no stable compounds of these elements are known. The ionization energies of krypton and xenon are lower but still very high; consequently only highly electronegative elements (F, O, and Cl) can form stable compounds with xenon and krypton without being oxidized themselves. Xenon reacts directly with only two elements: F2 and Cl2. Although XeCl2 and KrF2 can be prepared directly from the elements, they are substantially less stable than the xenon fluorides. Note the Pattern The ionization energies of helium, neon, and are so high that no stable compounds of these elements are known. Because halides of the noble gases are powerful oxidants and fluorinating agents, they decompose rapidly after contact with trace amounts of water, and they react violently with organic compounds or other reductants. The xenon fluorides are also Lewis acids; they react with the fluoride ion, the only Lewis base that is not oxidized immediately on contact, to form anionic complexes. For example, reacting cesium fluoride with XeF6 produces CsXeF7, which gives Cs2XeF8 when heated: