Abstract: When liquid ⁴He is cooled below 2.176 K, it undergoes a phase transition—Bose–Einstein condensation—and becomes a super- fluid with zero viscosity. Once in such a state, it can flow without dissipation even through pores of atomic dimensions. Although it is intuitive to associate superflow only with the liquid phase, it has been proposed theoretically that superflow can also occur in the solid phase of ⁴He. Owing to quantum mechanical fluctuations, delocalized vacancies and defects are expected to be present in crystalline solid ⁴He, even in the limit of zero temperature. These zero-point vacancies can in principle allow the appearance of superfluidity in the solid. However, in spite of many attempts, such a 'supersolid' phase has yet to be observed in bulk solid ⁴He. Here we report torsional oscillator measurements on solid helium confined in a porous medium, a configuration that is likely to be more heavily populated with vacancies than bulk helium. We find an abrupt drop in the rotational inertia5 of the confined solid below a certain critical temperature. The most likely interpretation of the inertia drop is entry into the supersolid phase. If confirmed, our results show that all three states of matter—gas, liquid and solid—can undergo Bose–Einstein condensation.

Probable observation of a supersolid helium phase, Kim, E., and Chan M. H. W. , Nature, 1/2004, Volume 427, Issue 6971, p.225 - 227, (2004)

Here is a list of the elements sorted by atomic number.

Element name	Element symbol	Atomic number
Hydrogen	H	1
Helium	He	2
Lithium	Li	3

The JANET periodic table.

Group															3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	1	2
Period
1																															1 H	2 He
1																															3 Li	4 Be
2																									5 B	6 C	7 N	8 O	9 F	10 Ne	11 Na	12 Mg
3																									13 Al	14 Si	15 P	16 S	17 Cl	18 Ar	19 K	20 Ca
4															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	37 Rb	38 Sr
5															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	55 Cs	56 Ba
6	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	87 Fr	88 Ra
7	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 Cp	113 Uut	114 Uuq	115 Uup	116 Uuh	117 Uus	118 Uuo	119 Uue	120 Ubn

Here is a list of the elements sorted by element symbol.

Element name	Element symbol	Atomic number
Actinium	Ac	89
Silver	Ag	47
Aluminium (aluminum)	Al	13
Americium	Am	95
Argon	Ar	18
Arsenic	As	33
Astatine	At	85
Gold	Au	79
Boron	B	5
Barium	Ba	56
Beryllium	Be	4
Bohrium	Bh	107
Bismuth	Bi	83
Berkelium	Bk	97
Bromine	Br	35
Carbon	C	6
Calcium	Ca	20
Cadmium	Cd	48
Cerium	Ce	58
Californium	Cf	98
Chlorine	Cl	17
Curium	Cm	96
Cobalt	Co	27
Copernicium	Cp	112
Chromium	Cr	24
Caesium (Cesium)	Cs	55
Copper	Cu	29
Dubnium	Db	105
Darmstadtium	Ds	110
Dysprosium	Dy	66
Erbium	Er	68
Einsteinium	Es	99
Europium	Eu	63
Fluorine	F	9
Iron	Fe	26
Fermium	Fm	100
Francium	Fr	87
Gallium	Ga	31
Gadolinium	Gd	64
Germanium	Ge	32
Hydrogen	H	1
Helium	He	2
Hafnium	Hf	72
Mercury	Hg	80
Holmium	Ho	67
Hassium	Hs	108
Iodine	I	53
Indium	In	49
Iridium	Ir	77
Potassium	K	19
Krypton	Kr	36
Lanthanum	La	57
Lithium	Li	3
Lawrencium	Lr	103
Lutetium	Lu	71
Mendelevium	Md	101
Magnesium	Mg	12
Manganese	Mn	25
Molybdenum	Mo	42
Meitnerium	Mt	109
Nitrogen	N	7
Sodium	Na	11
Niobium	Nb	41
Neodymium	Nd	60
Neon	Ne	10
Nickel	Ni	28
Nobelium	No	102
Neptunium	Np	93
Oxygen	O	8
Osmium	Os	76
Phosphorus	P	15
Protactinium	Pa	91
Lead	Pb	82
Palladium	Pd	46
Promethium	Pm	61
Polonium	Po	84
Praseodymium	Pr	59
Platinum	Pt	78
Plutonium	Pu	94
Radium	Ra	88
Rubidium	Rb	37
Rhenium	Re	75
Rutherfordium	Rf	104
Roentgenium	Rg	111
Rhodium	Rh	45
Radon	Rn	86
Ruthenium	Ru	44
Sulfur (Sulphur)	S	16
Antimony	Sb	51
Scandium	Sc	21
Selenium	Se	34
Seaborgium	Sg	106
Silicon	Si	14
Samarium	Sm	62
Tin	Sn	50
Strontium	Sr	38
Tantalum	Ta	73
Terbium	Tb	65
Technetium	Tc	43
Tellurium	Te	52
Thorium	Th	90
Titanium	Ti	22
Thallium	Tl	81
Thulium	Tm	69
Uranium	U	92
Ununhexium	Uuh	116
Ununoctium	Uuo	118
Ununpentium	Uup	115
Ununquadium	Uuq	114
Ununseptium	Uus	117
Ununtrium	Uut	113
Vanadium	V	23
Tungsten	W	74
Xenon	Xe	54
Yttrium	Y	39
Ytterbium	Yb	70
Zinc	Zn	30
Zirconium	Zr	40

Here is a list of the elements sorted by alphabetically by element name.

Element name	Element symbol	Atomic number
Actinium	Ac	89
Aluminium (aluminum)	Al	13
Americium	Am	95
Antimony	Sb	51
Argon	Ar	18
Arsenic	As	33
Astatine	At	85
Barium	Ba	56
Berkelium	Bk	97
Beryllium	Be	4
Bismuth	Bi	83
Bohrium	Bh	107
Boron	B	5
Bromine	Br	35
Cadmium	Cd	48
Caesium (Cesium)	Cs	55
Calcium	Ca	20
Californium	Cf	98
Carbon	C	6
Cerium	Ce	58
Chlorine	Cl	17
Chromium	Cr	24
Cobalt	Co	27
Copernicium	Cp	112
Copper	Cu	29
Curium	Cm	96
Darmstadtium	Ds	110
Dubnium	Db	105
Dysprosium	Dy	66
Einsteinium	Es	99
Erbium	Er	68
Europium	Eu	63
Fermium	Fm	100
Fluorine	F	9
Francium	Fr	87
Gadolinium	Gd	64
Gallium	Ga	31
Germanium	Ge	32
Gold	Au	79
Hafnium	Hf	72
Hassium	Hs	108
Helium	He	2
Holmium	Ho	67
Hydrogen	H	1
Indium	In	49
Iodine	I	53
Iridium	Ir	77
Iron	Fe	26
Krypton	Kr	36
Lanthanum	La	57
Lawrencium	Lr	103
Lead	Pb	82
Lithium	Li	3
Lutetium	Lu	71
Magnesium	Mg	12
Manganese	Mn	25
Meitnerium	Mt	109
Mendelevium	Md	101
Mercury	Hg	80
Molybdenum	Mo	42
Neodymium	Nd	60
Neon	Ne	10
Neptunium	Np	93
Nickel	Ni	28
Niobium	Nb	41
Nitrogen	N	7
Nobelium	No	102
Osmium	Os	76
Oxygen	O	8
Palladium	Pd	46
Phosphorus	P	15
Platinum	Pt	78
Plutonium	Pu	94
Polonium	Po	84
Potassium	K	19
Praseodymium	Pr	59
Promethium	Pm	61
Protactinium	Pa	91
Radium	Ra	88
Radon	Rn	86
Rhenium	Re	75
Rhodium	Rh	45
Roentgenium	Rg	111
Rubidium	Rb	37
Ruthenium	Ru	44
Rutherfordium	Rf	104
Samarium	Sm	62
Scandium	Sc	21
Seaborgium	Sg	106
Selenium	Se	34
Silicon	Si	14
Silver	Ag	47
Sodium	Na	11
Strontium	Sr	38
Sulfur (Sulphur)	S	16
Tantalum	Ta	73
Technetium	Tc	43
Tellurium	Te	52
Terbium	Tb	65
Thallium	Tl	81
Thorium	Th	90
Thulium	Tm	69
Tin	Sn	50
Titanium	Ti	22
Tungsten	W	74
Ununhexium	Uuh	116
Ununoctium	Uuo	118
Ununpentium	Uup	115
Ununquadium	Uuq	114
Ununseptium	Uus	117
Ununtrium	Uut	113
Uranium	U	92
Vanadium	V	23
Xenon	Xe	54
Ytterbium	Yb	70
Yttrium	Y	39
Zinc	Zn	30
Zirconium	Zr	40

Sponsoring an element

The visible form of the sponsorship can be along the following lines (but if this is not what you had in mind, we may be able to work together towards your needs):

• banner ad (468 x 60 pixels) at top of all pages for that element
• additional small graphic button (120 x 60 pixels) on the left menu panel
• small "advertorial" on an appropriate page for that element, 30-60 words and a small image, set in a panel on that page.

In each case, we can direct users to an appropriate page within your own site.

WebElements user profile

WebElements users are intelligent and well-educated. According to an online survey responded to by 25000 users:

• about 65% of all users are from USA
• about 60% of all users are under 21 (average age 24, median age 16-17)
• about 50% of all users over 21 are degree holders
• the overall male:female ratio of users is almost exactly 50:50 (more female in younger age groups, more male in older age groups

If you are interested in sponsoring an element, or just adding to WebElements content, please contact WebElements in the first instance.

Table 1. Table of element "popularities" relative to hydrogen = 100

Element	Popularity	Element	Popularity	Element	Popularity
actinium	22	holmium	14	rhodium	21
aluminium	80	hydrogen	100	rubidium	25
americium	18	indium	25	ruthenium	22
antimony	26	iodine	39	rutherfordium	12
argon	41	iridium	23	samarium	15
arsenic	42	iron	72	scandium	29
astatine	19	krypton	39	seaborgium	13
barium	31	lanthanum	18	selenium	28
berkelium	14	lawrencium	13	silicon	65
beryllium	45	lead	48	silver	68
bismuth	23	lithium	64	sodium	76
bohrium	12	lutetium	16	strontium	26
boron	54	magnesium	63	sulphur	57
bromine	33	manganese	35	tantalum	22
cadmium	24	meitnerium	12	technetium	21
caesium	27	mendelevium	12	tellurium	21
calcium	69	mercury	54	terbium	14
californium	17	molybdenum	29	thallium	21
carbon	82	neodymium	16	thorium	16
cerium	18	neon	61	thulium	13
chlorine	57	neptunium	16	tin	43
chromium	45	nickel	50	titanium	62
cobalt	42	niobium	23	tungsten	34
copper	71	nitrogen	69	ununbium	12
curium	14	nobelium	13	ununhexium	14
dubnium	12	osmium	22	ununnilium	12
dysprosium	15	oxygen	73	ununoctium	22
einsteinium	18	palladium	24	ununpentium	5
erbium	15	phosphorus	51	ununquadium	15
europium	17	platinum	57	ununseptium	5
fermium	11	plutonium	28	ununtrium	5
fluorine	45	polonium	19	roentgenium	13
francium	20	potassium	65	uranium	40
gadolinium	16	praseodymium	16	vanadium	31
gallium	30	promethium	13	xenon	30
germanium	30	protactinium	13	ytterbium	15
gold	76	radium	25	yttrium	21
hafnium	18	radon	25	zinc	53
hassium	11	rhenium	20	zirconium	27
helium	58

The BBC is airing some "periodic tales" on Radio 4. Familiar Radio 4 voices introduce elements from the Periodic Table and the unique roles they play in human existence - with a little help from the irreverent Tom Lehrer. Listen to these ten elements:

• Krypton: Heidli Nicklaus on the Superman element, krypton
• Helium: Brian Perkins dramatises the effects of Helium
• Silver: Trevor Harrison (Eddie Grundy in the Archers) finds some unusual properties of Silver
• Cobalt: Hedli Nicklaus (Cathy Perks) takes on the goblin element of cobalt
• Selenium: Carole Boyd (The Archers' Linda Snell) unearths selenium
• Oxygen: Brian Perkins bravely dramatises the effects of oxygen
• Arsenic: Charlotte Green takes on the deadly history of arsenic
• Mercury: Carole Boyd (Linda Snell) reflects on mercury, the poisonous liquid metal
• Iodine: Charlotte Green on the discovery of iodine's essential place in brain development
• Nickel: Trevor Harrison reveals that the space station Mir is largely made of nickel

[[Note added Dec 2009: sadly these recordings no longer exist on the BBC site. I did offer to host them here but no luck]]

In a letter to Nature E. Kim and M. H. W. Chan (Pennsylvania State University, USA) note that when liquid ⁴He is cooled below 2.176 K, it undergoes a phase transition and becomes a superfluid with zero viscosity. They claim that in addition to superflow in the liquid phase, superflow can also occur under some conditions in the solid phase of one of the helium isotopes (⁴He), and present results to back this up. In other words - evidence for a "supersolid". A supersolid behaves like a superfluid (flows without resistance) although it has crystalline solid characteristics.1

• 1. Probable observation of a supersolid helium phase,
  Kim, E., and Chan M. H. W.
  , Nature, 1/2004, Volume 427, Issue 6971, p.225 - 227, (2004)
  

Earth's most severe mass extinction - an event 250 million years ago that wiped out 90 percent of all marine species and 70 percent of land vertebrates - was triggered by a collision with a comet or asteroid, according to a team led by The University of Washington, Seattle, USA. Evidence is based upon elegant findings involving carbon molecules called buckminsterfullerenes (C₆₀, Buckyballs) with the gases helium and argon trapped inside their cage structures.

The scientists do not know the site of the impact 250 million years ago, when all Earth's land formed a supercontinent called Pangea. However, the space body left a calling card - a much higher level of complex carbon molecules called buckminsterfullerenes, or Buckyballs, with the noble (or chemically nonreactive) gases helium and argon trapped inside their cage structures. Fullerenes, which contain 60 or more carbon atoms and have a structure resembling a soccer ball or a geodesic dome, are named for Buckminster Fuller, who invented the geodesic dome.

The researchers know these particular Buckyballs are extraterrestrial because the noble gases trapped inside have an unusual ratio of isotopes. For instance, terrestrial helium is mostly helium-4 and contains only a small amount of helium-3, while extraterrestrial helium - the kind found in these fullerenes - is mostly helium-3.

"These things form in carbon stars. That's what's exciting about finding fullerenes as a tracer," according to Luann Becker, one of scientific team involved. The extreme temperatures and gas pressures in carbon stars are perhaps the only way extraterrestrial noble gases could be forced inside a fullerene, she said. These gas-laden fullerenes were formed outside the Solar System, and their concentration at the Permian-Triassic boundary means they were delivered by a comet or asteroid.