Protactinium

Protactinium
Atomic Number	91
Category	Actinide

Protactinium, Pa, is the name of element 91. Four of its isotopes are present in uranium ores. ²³¹Pa results from decay of ²³⁵U. ²³¹Pa is by far the longest-lived isotope of Pa, with a half-life of 3.27E04 years⁽¹⁾. It's long life makes it the only isotope which is present in uranium ores in technically recoverable amounts. ²³⁴Pa and its excited state (isomer), ^234mPa, result from alpha decay of ²³⁸U. ²³³Pa is produced by decay of ²³⁷Np formed by the rare (1 per 2 million decays) spontaneous fission of ²³⁸U. (See "Uranium", this wiki, for details.)

Neither the most neutron-rich (heaviest) nor neutron-poor (lightest) isotopes of this element have been observed⁽²⁾, although around 35 isotopes or isomers have been. The number is a bit uncertain because the observations listed include two isotopes whose key properties are derived from theory rather than observation. Their properties are, therefore, less reliable than is true for fully-observed isotopes. What can be said with confidence is that only 8 of them have half-lives longer than an hour.

Pa is only expected to form in a core collapse supernova or a neutron star merger (kilonova). Within 10 years after such an event, only ²³¹Pa will remain from the original material. Original ²³¹Pa will persist for about 3 million years, not quite long enough for it to exist in planetesimals. In terrestrial planets, ²³¹Pa, ²³³Pa, ²³⁴Pa, and ^234mPa exist in equilibrium with ²³⁵U and ²³⁸U.

The element is an actinide, chemically similar to U and Th. While its chemistry has been studied in detail, the element's nuclear properties are of greater importance in most situations.

NUCLEAR POWER

Many uranium ores contain an appreciable amount of thorium. If thorium is present, neutron capture by ²³²Th will produce ²³³Th, which decays through ²³³Pa to ²³³U. If Th is not present the only source of ²³³Pa is alpha decay from ²³⁷Np.

Transmutation of ²³²Th into ²³³U can also be done by exposing Th to reactor neutrons and separating the resulting ²³³U for use as fuel.

02-27-21

REFERENCES

1. Wikipedia. most information in this article is extracted from Wikipedia.
2. "Decay Modes and a Limit of Existence of Nuclei", Hiroyuki Koura, 4th International Conference on the Chemistry and Physics of the Transactinide Elements.

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

(02-16-22)