6. It's elemental, Watson! And here's your second clue: this element was discovered in 1878 by J.L. Soret, and one isotope has a half-life of 1.1 days. What element is this?
From Quiz Holy Hairspray, it's the "H" Quiz!
Answer:
Holmium
Holmium (Ho) was not really named after Sherlock. Found in gadolinite and used in nuclear reactors, it's silver, hexagonal and classified as a rare earth. It's atomic number is 67, atomic mass is 164.93031 amu, melting point is 2678 degrees F, and it has four isotopes.
Hafnium (Hf) really does exist, it's not just a stoner's way to say the glass isn't full... Discovered in 1923 by a chap named Dirk Coster, it finally found a use in nuclear reactors. The element is found in zircon, has ten isotopes with halflives ranging from 70 days to stability, has an atomic number of 72 and an atomic mass of 178.49 amu and a melting point of 3902 degrees F. This 'hot stuff' element is silver coloured and is hexagonal in shape.
Helium (He)is a noble gas best known for producing a voice like Donald Duck. Actually, it is used mostly in filling balloons and in deep sea diving. It was first identified in 1895 by Sir William Ramsay, is atomic number 2, has a mass of 4.002602 amu, a melting point of -457.6 F (yup, that means it is a gas, unless you have a really really cold freezer!), has two isotopes which are both stable (ie, no half lives here) and is hexagonal and colourless.
Hydrogen is element number 1 - it's the lightest one on the periodic block. It is in air, and with oxygen forms water (just in case you slept though chem 101). With an atomic mass of 1.00794 amu, it is used in metal refining and yes, for filling balloons (where would civilisation be without those balloons?), and hopefully will someday become a reliable and common power source for cars. It was identified in 1766 by Henry Cavendish, has three isotopes, two of which are stable and the other has a half life of 12.3 years, melts at -434.45203 degrees F (another colourless gas) and is hexagonal.