Mercury

An example of a mercury sample.

Mercury is a chemical element with symbol Hg and atomic number 80. It is commonly known as quicksilver and was formerly named hydrargyrum (/haɪˈdrɑrdʒərəm/), from which its symbol comes. A heavy, silvery d-block element, mercury is the only metallic element that is liquid at standard conditions for temperature and pressure; the only other element that is liquid under these conditions is bromine, though elements such as caesium, gallium, and rubidium melt just above room temperature. It should be noted that a number of alloys are liquid at STP.

Mercury occurs in deposits throughout the world mostly as cinnabar (Mercuric sulfide). The red pigment vermilion, a pure form of mercuric sulfide, is mostly obtained by reaction of mercury (produced by reduction from cinnabar) with sulfur. Mercury poisoning can result from exposure to water-soluble forms of mercury (such as Mercuric chloride or methylmercury), inhalation of mercury vapor, or eating seafood contaminated with mercury.

Mercury is used in thermometers, barometers, manometers, sphygmomanometers, float valves, mercury switches, mercury relays, fluorescent lamps and other devices, though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinical environments in favour of alternatives such as alcohol- or galinstan-filled glass thermometers and thermistor- or infrared-based electronic instruments. Likewise, mechanical pressure gauges and electronic strain gauge sensors have replaced mercury sphygmomanometers. Mercury remains in use in scientific research applications and in amalgam material for dental restoration in some locales. It is used in lighting: electricity passed through mercury vapor in a fluorescent lamp produces short-wave ultraviolet light which then causes the phosphor in the tube to fluoresce, making visible light.

Among the things not known about mercury is the concentration of mercury on Mercury.

Isotopes and formation

At least 104 isotopes of mercury have been predicted, ranging from near ²⁶⁴Hg down to ¹⁶¹Hg. The heaviest of these has N = 184, a "magic" number, and the lightest has N = 81 , one less than the shell closure at N = 82. Of the isotopes predicted, 47 have been observed, as well as 16 isomers.

All Hg isotopes heavier than 204Hg decay solely by beta emission with short half-lives. Between ²⁰⁴Hg and ¹⁹⁶Hg has 7 effectively and observationally stable isotopes and two radioactive ones - ²⁰³Hg and ¹⁹⁷Hg. The former decays purely by beta emission and has a half-life of 46.6 days, second longest among Hg isotopes. The latter has two isomers; ¹⁹⁷Hg, which decays by electron capture with a 64.14 hr half-life, and ^197mHg, which has a half-life of 23.8 hrs and decays mainly [branch ratio (BR) = 0.914] by isomeric transition to its ground state (but has an electron capture branch with BR = 0.086).

¹⁹⁴Hg has a 447 +/- 52 year half life. [Wikipedia reports 444 +/- 77 yr half-life.] and decays by electron capture with a decay energy of 28 keV. Its decay isn't inhibited, simply weak - which is to be expected at its location. Other than it, positive beta decay (positron emission or electron capture) sets in at ¹⁹⁵Hg and is observed down to ¹⁷⁶Hg. Alpha decay becomes active at ¹⁹²Hg, although it is very weak down to ¹⁸⁷Hg (and nonexistent in ¹⁹¹Hg). Alpha decay becomes dominant at ¹⁷⁹Hg and the only mode of decay between ¹⁷⁵Hg and ¹⁶⁴Hg. Proton decay is predicted for ¹⁶³Hg to ¹⁶¹Hg. ¹⁸³Hg to ¹⁷⁹Hg are also reported to exhibit positron + proton decay (always a weak branch). Half-lives decline as expected below ¹⁹⁶Hg.

Mercury isotopes ¹⁹⁹Hg and heavier can form via beta-decay chains from initially neutron-rich nuclides produced by a rapid series of neutron captures in a supernova or neutron star merger or ejected from a disintegrating neutron star. In addition, slow capture of neutrons by Pt can produce ¹⁹⁸Hg as well as ²⁰²Hg to ¹⁹⁹Hg. Other mechanisms produce the light stable isotope ¹⁹⁶Hg, as well as radioactive Hg isotopes which have disappeared. In the most probable of these, a mercury nucleus captures a gamma photon which causes it to eject a neutron. Isotopic fraction of ¹⁹⁶Hg is 0.000015, which indicates how weak gamma capture is as a means of forming nuclei.

References

9-Period Periodic Table of Elements
1	1 H																																																																	2 He
2	3 Li	4 Be																																																																	5 B	6 C	7 N	8 O	9 F	10 Ne
3	11 Na	12 Mg																																																																	13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
4	19 K	20 Ca																																																																	21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
5	37 Rb	38 Sr																																																																	39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
6	55 Cs	56 Ba																																																					57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb	71 Lu	72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
7	87 Fr	88 Ra																																																					89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No	103 Lr	104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Cn	113 Nh	114 Fl	115 Mc	116 Lv	117 Ts	118 Og
8	119 Uue	120 Ubn																															121 Ubu	122 Ubb	123 Ubt	124 Ubq	125 Ubp	126 Ubh	127 Ubs	128 Ubo	129 Ube	130 Utn	131 Utu	132 Utb	133 Utt	134 Utq	135 Utp	136 Uth	137 Uts	138 Uto	139 Ute	140 Uqn	141 Uqu	142 Uqb	143 Uqt	144 Uqq	145 Uqp	146 Uqh	147 Uqs	148 Uqo	149 Uqe	150 Upn	151 Upu	152 Upb	153 Upt	154 Upq	155 Upp	156 Uph	157 Ups	158 Upo	159 Upe	160 Uhn	161 Uhu	162 Uhb	163 Uht	164 Uhq	165 Uhp	166 Uhh	167 Uhs	168 Uho	169 Uhe	170 Usn	171 Usu	172 Usb
9	173 Ust	174 Usq
Alkali metal Alkaline earth metal Lanthanide Actinide Superactinide Transition metal Post-transition metal Metalloid Other nonmetal Halogen Noble gas predicted predicted predicted predicted predicted predicted predicted predicted predicted

(03-03-22)