Gold

Gold (Aurum in Latin) is a soft golden metal with 79 protons, it's atomic symbol is Au.

Properties

Gold has the third-highest electrical conductivity among elements, following silver and copper..

It is highly chemically inert compared to most elements, Specifically, compounds of gold and oxygen are endothermic - such compounds will decompose spontaneously to produce elemental gold. It does form alloys, notably with other Group 11 metals copper and silver. It also alloys with mercury.

Although most gold in earth's crust exists as flecks of reduced metal, physically located within a mineral matrix but not chemically a part of it, there are a few minerals of gold. Notable in this context are gold telluride (AuTe2) ores, although gold-bearing minerals of bismuth and arsenic are known as well as alloys containing such intermetallic compounds such as Cu₃Au.

Uses

It's used in gold foil (hence gold foil), fillings, microchips, wire, etc. It's chemical inertness and good electrical conductivity have led to an important new application. Modern credit / debit cards must connect electrically to card readers. The yellow patch on such cards is a thin layer of gold.

The resistance of gold to oxidation accounts for its use in electrical connectors. Most metals will form an oxide film in air. If a small electrical signal (millivolt / microamp) passes through that connector, it does not have enough energy to disrupt the film - in substance, the connector acts like a capacitor, distorting the signal. A gold-surfaced connector remains clean, allowing even low-level signals to pass through without distortion.

Nuclear Properties and Formation

Approximately 96 isotopes of gold are predicted to exist, of which 38 have been observed (plus 40 isomers). Heavy isotopes of gold, ¹⁹⁸Au and greater, decay quickly by beta emission. The longest-lived heavy isotope, ¹⁹⁹Au has the longest half-life at 3.14 days, which is to be expected. ¹⁹⁷Au is gold's only stable isotope, which is a bit unusual, Most high-Z, odd-Z elements have two, or at least one stable and one almost stable, isotopes. Light isotopes have a positive beta decay (positron emission or electron capture) branch between ¹⁹⁶Au and ¹⁷³Au. Alpha decay appears as very weak branches at ¹⁹³Au and ¹⁹⁰Au through ¹⁸⁶Au, but does not become significant until ¹⁸⁵Au. Between ¹⁸⁵Au and ¹⁷⁷Au, alpha decay is a minor branch, below which it becomes dominant down to ¹⁷²Au. Between ¹⁷¹Au and ¹⁶⁶Au, proton decay is dominant.

Gold is largely produced in supernovae and neutron star mergers via beta-decay chains originating in neutron-rich nuclei either produced by a rapid series of neutron captures (r process) or ejected directly from a disintegrating neutron star. Some is also produced in highly-evolved stars by a slower sequence of neutron captures mixed with beta decay (s process). The key reaction here is neutron capture by ¹⁹⁶Pt followed by beta decay of ¹⁹⁷Pt (20 hr half-life).

A comparison of solar system and crustal abundances of odd-Z elements between Tl and Lu indicates that gold is severely depleted in earth's crust. This is a consequence of its chemical inertness and gold's ability to dissolve in liquid iron. Gold is uncommon in the solar system (although more abundant than either Bi or W), but very rare in earth's crust. Most minable gold appears to have been brought up from the mantle.

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