Radium

Radium
88Ra
Ba ↑ Ra ↓ Ubn Periodic table Francium ← radium → Actinium
Appearance
General properties
Name, symbol, number	radium, Ra, 88
Element category	alkaline earth metals
Group, period, block	2, 7, s
Standard atomic weight	226.0273
Electron configuration	[Rn] 7s2 2, 8, 18, 32, 18, 8, 2 File:Electron shell 088 Radium - no label.svg.png
History
Discovery	Pierre Curie and Marie Curie (1898)
First isolation	Marie Curie (1902)
Physical properties
Phase	soild
Density (near r.t.	(0 °C, 101.325 kPa) 5.5 g/cm3
Melting point	973 K
Boiling point	2010 K
Heat of fusion	8.5 kJ·mol-1
Heat of vaporization	113 kJ·mol-1
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 819 906 1037 1209 1446 1799
Atomic properties
Oxidation states	2+
Electronegativity	0.9 (Pauling Scale)
Ionization energies	509.3 KJ/mol
Atomic radius	215 pm
Covalent radius	221±2 pm
Van der Waals radius	283 pm
Crystal structure	Cubic body centered
Magnetic ordering	Nonmagnetic
Electrical resistivity	(20 °C) 1 µΩ·m
Thermal conductivity	(300 K) 18.6 mW/(m/K)
CAS registry number	7440-14-4
v • t • e • r

The NEW Periodic Table Song (In Order)

Radium is a chemical element with symbol Ra and atomic number 88. Radium is an almost pure-white alkaline earth metal, but turns black on exposure to air. This unusual color occurs because Ra reacts with nitrogen rather than oxygen in the air. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226, which has a half-life of 1600 (+/- 7) years and decays into ²²²Rn.

Since the only radium isotopes existing in the earth today are within decay chains of the long-lived nuclides ²³²Th, ²³⁵U, and ²³⁸U, it is possible to provide a standard atomic weight for radium that will not change in the forseeable future. There are four current radium isotopes: ²²⁸Ra, ²²⁶Ra, ²²⁴Ra, and ²²³Ra. Two other isotopes are reported to be present, but they are daughters of ²³⁷Np. ²³⁷Np itself forms via two neutron captures (and substantial loss due to induced fission of ²³⁵U. using neutrons provided by the rare spontaneous fission branch of ²³⁸U. Production of ²²⁵Ra and ²²¹Ra is lost in the noise of things which happen too rarely to care about.

Half-lives and branching ratios are accurately known for all four isotopes. An overall branch ratio from its chain head to each Ra isotope can be computed by multiplying individual branch ratios at each step in a chain of transmutations from head to the target Ra isotope and summing where possible decay paths diverge and recombine. Equilibrium occurs when the target isotope decays at a rate equal to the chain head's decay rate times the overall branch ratio from head to target. Equilibrium (atomic) concentration is overall branch ratio multiplied by half-life of the target divided by half-life of the head. Atomic masses are also known with precision for all four Ra isotopes. Normalizing concentration to 1 and multiplying normalized concentration of each isotope by its atomic mass gives a set of partial masses which can be summed to give the overall atomic weight reported in the infobox.

Radium, in the form of radium chloride, was discovered by Marie Curie and Pierre Curie in 1898. They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1910. Between radium's discovery and acceptance of our current model of the nucleus, people gave names like radium A and radium C2 to several isotopes of other elements that are decay products of radium-226.

In nature, radium is found in uranium ores in trace amounts (up to 1/7 gram per ton of uraninite). Radium is not necessary for living organisms, and adverse health effects are likely when it is incorporated into biochemical processes because of its radioactivity and chemical reactivity. It should be noted that uranium is present in most surface rocks and soils at around the one atom per million level. There are no branches in the decay chain from ²³⁸U to ²²⁶Ra, so the Ra/U molar concentration ratio equals the ratio of their half-lives, which means ²²⁶Ra is present in most surface rocks in soils - at a concentration under a part per trillion.

There are reports of Ra leaching into drilling mud. Even if it is enriched by a factor of 1000, it's present in less than a part per billion - which is on the order of magnitude for limiting concentration in ambient air of agents such as VX or GB (Sarin). While its concentration can rise well above the parts per billion level, that can only happen if a boring passes through a uranium-rich zone, something likely to be of interest to those funding the boring.

Radium has been predicted to form isotopes between the neutron dripline at approximately ²⁹⁵Ra down to ¹⁸⁶Ra, of which those isotopes between ²³⁴Ra and ²⁰²Ra (as well as 12 isomers) have been observed. ²²⁷Ra and heavier isotopes decay by beta emission. Except for ²²⁸Ra, all half-lives are less than 94 minutes and all but two are less than 5 minutes. ²²⁵Ra also beta-decays, with a relatively long half-life of 14.9 days. Between ²²²Ra and ²¹⁵Ra all isotopes decay exclusively by alpha emission and have half-lives under 40 sec. (This reflects instability above the neutron shell closure at N = 126.) At ²¹⁴Ra, positron decay appears as an alternative mode to alpha decay. As A declines, half-lives and positron-emission branch ratios decline until decay is purely alpha emission. The very lightest Ra isotopes decay by proton emission.

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