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 2006-02-16, 17:06 #1 davar55     May 2004 New York City 2·32·5·47 Posts Elemental Puzzle Here's an easy one: What do these five elements, and no others, have in common? Hg, Kr, Np, Pu, and U.
 2006-02-16, 17:48 #2 mfgoode Bronze Medalist     Jan 2004 Mumbai,India 22×33×19 Posts Elemental Puzzle This seems to be more chemistry than math. Nevertheless the last three are actinides, Hg is liquid at N.T.P. Kr is a rare gas and U is radioactive. I fail to see a chemical connection so I pass. Mally
2006-02-16, 20:11   #3
xilman
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Quote:
 Originally Posted by davar55 Here's an easy one: What do these five elements, and no others, have in common? Hg, Kr, Np, Pu, and U.
You forgot Te.

I could make a good case for including Ce, Se and He too.

Paul

 2006-02-16, 20:25 #4 Citrix     Jun 2003 110001001112 Posts Are you asking about chemical properties or mathematical properties of their atomic mass or number?
 2006-02-16, 20:53 #5 THILLIAR     Mar 2004 ARIZONA, USA 23 Posts Hg: Atomic number - 80 Density g/mL 13 .53 Atomic weight u 200 .59 Melting point K 234 .28 Bonding radius A 1 .49 Boiling point K 630 Atomic radius A 1 .76 Heat of vaporization kJ/mol 59 .229 Ionization Potential V 10 .437 Heat of fusion kJ/mol 2 .295 Electronegativity - 2 Specific heat J/gK 0 .139 The oxide is mildly basic. Crystal are rhombohedral. Kr: Atomic number - 36 Density g/L 3 .74 Atomic weight u 83 .8 Melting point K 115 .78 Bonding radius A 1 .12 Boiling point K 119 .8 Atomic radius A 1 .03 Heat of vaporization kJ/mol 9 .029 Ionization Potential V 13 .999 Heat of fusion kJ/mol 1 .638 Electronegativity - - Specific heat J/gK 0 .248 The oxide is unknown. Crystal are face centered cubic. Np: Atomic number - 93 Density g/mL 20 .4 Atomic weight u 237 .0482 Melting point K 910 Bonding radius A - Boiling point K - Atomic radius A - Heat of vaporization kJ/mol - Ionization Potential V 6 .19 Heat of fusion kJ/mol 5 .19 Electronegativity - 1 .36 Specific heat J/gK 0 .12 The oxide is amphoteric. Crystal are orthorhombic. Pu: Atomic number - 94 Density g/mL 19 .8 Atomic weight u 244 Melting point K 913 Bonding radius A - Boiling point K 3503 Atomic radius A - Heat of vaporization kJ/mol 344 Ionization Potential V 6 .06 Heat of fusion kJ/mol 2 .84 Electronegativity - 1 .28 Specific heat J/gK 0 .13 The oxide is amphoteric. Crystal are monoclinic. U: Atomic number - 92 Density g/mL 18 .9 Atomic weight u 238 .029 Melting point K 1405 Bonding radius A 1 .42 Boiling point K 4407 Atomic radius A - Heat of vaporization kJ/mol 477 Ionization Potential V 6 .05 Heat of fusion kJ/mol 8 .52 Electronegativity - 1 .38 Specific heat J/gK 0 .12 The oxide is amphoteric. Crystal are orthorhombic.
2006-02-16, 21:27   #6
xilman
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Quote:
 Originally Posted by Citrix Are you asking about chemical properties or mathematical properties of their atomic mass or number?
I don't think it's giving much away to reveal that the answer to your question is "no".

I've already indicated that I know the desired answer. If that isn't a big enough hint, you're in difficulties.

Paull

2006-02-16, 21:29   #7
xilman
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Quote:
 Originally Posted by THILLIAR Kr: ... The oxide is unknown.
I'm not entirely sure of that. I'll look it up.

Oxides of xenon were characterized many years ago. Other krypton compounds are well known.

Paul

2006-02-16, 21:42   #8
Citrix

Jun 2003

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Quote:
 Originally Posted by xilman I don't think it's giving much away to reveal that the answer to your question is "no". I've already indicated that I know the desired answer. If that isn't a big enough hint, you're in difficulties. Paull
No to what? (No to a mathematical pattern or a chemical pattern)

 2006-02-16, 22:08 #9 akruppa     "Nancy" Aug 2002 Alexandria 246710 Posts Mercury, Neptunium, Plutonium and Uranium are all named after celestial bodies, planets of our solar system in this case (or the deities of the same name). Krypton does not seem to fit in, unless you count Superman's home planet... Tellur does not seem to fit, either. Cerium is probably named after Ceres, an asteroid. Helium is probably named after Helios, greek for sun. But I didn't check if any other elements are named after celestial bodies/deities. Alex Last fiddled with by akruppa on 2006-03-11 at 19:25 Reason: fubar grammar
2006-02-16, 22:18   #10
xilman
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Quote:
 Originally Posted by akruppa Mercury, Neptunium, Plutonium and Uranium are all named after celestial bodies, planets of our solar system in this case (or the deities of the same name). Krypton does seem not fit in, unless you count Superman's home planet... Tellur does not seem to fit, either. Cerium is probably named after Ceres, an asteroid. Helium is probably named after Helios, greek for sun. But I didn't check if any other elements are named after celestial bodies/deities. Alex
Look up Tellus, telluric, and a whole bunch of similarly derived words.

While your are consulting your dictionary and encyclopaedias, check out Selene, selenography, selenographic and other such words.

Cerium was discovered in 1801, the same year as the world Ceres. The asteroid was found on the very first day of the nineteenth century and the element later that year.

Incidentally, roughly half of my DPhil research was spent investigating the properties of CeO in the gas phase. Fascinating molecule, if you like that sort of thing.

Paul

2006-02-16, 22:22   #11
xilman
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Quote:
 Originally Posted by akruppa Mercury, Neptunium, Plutonium and Uranium are all named after celestial bodies, planets of our solar system in this case (or the deities of the same name). Krypton does seem not fit in, unless you count Superman's home planet... Tellur does not seem to fit, either. Cerium is probably named after Ceres, an asteroid. Helium is probably named after Helios, greek for sun. But I didn't check if any other elements are named after celestial bodies/deities. Alex
AFAIK, U, Np and Pu are named after the planets. Hg, I'm not so sure but possibly the deity. Superman's home planet was named after the element.

Paul

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