- How did Ramsay use fractional distillation of liquid air to isolate neon, krypton, and xenon?
- Where did Ramsay find helium before he found it in the atmosphere?
- How did Mendeleev react to a new group of elements his periodic table had no place for?
- What did the noble gases have in common that made them a coherent chemical group rather than isolated curiosities?
Periodic Table and Element Discovery
The organization and discovery of the chemical elements.
- Which noble gas was still missing from the periodic table in 1904, and when did it turn up?
- Why was finding an element that doesn't react with anything actually difficult?
- How did the discovery of the noble gases force a revision of Mendeleev's original 1869 periodic table?
- How did the concept of isotopes resolve the paradox of radioactive decay series producing more 'elements' than the periodic table had room for?
- How did Kamerlingh Onnes manage to liquefy helium when no one had achieved it before?
- What anomalies in Mendeleev's atomic-weight ordering of the periodic table needed explaining?
- What did the integer steps in X-ray frequency reveal about the true ordering principle of the elements?
- How did Moseley's method allow him to predict undiscovered elements?
- Why were precise atomic weights necessary to validate Mendeleev's periodic table?
- Why does the number of protons in an atom's nucleus determine its position on the periodic table?
- What exceptions in Mendeleev's original ordering did Moseley's atomic number principle resolve?
- What problem in the periodic table led Frederick Soddy to propose the concept of isotopes?
- Why did chlorine's non-integer molar mass of 35.45 embarrass atomic theory for decades?
- What two isotopes of chlorine did Aston find, and in what ratio do they combine to average 35.45?
- How does the exclusion principle explain the structure of the periodic table, like why noble gases are inert?
- How did Noddack, Tacke, and Berg detect element 75 in molybdenite and columbite ore?
- Why is rhenium notable among naturally occurring elements in terms of when it was discovered?
- What property of rhenium makes it useful in jet engine turbine blades?
- How did Marguerite Perey identify element 87 in the decay products of actinium?
- Why is francium considered the last naturally occurring element to be discovered?
- Why did Mendeleev's original periodic table stop at uranium?
- What is the actinide series and why did Seaborg's proposed rearrangement of the periodic table matter?
- How did Albert Ghiorso's team at Berkeley synthesize lawrencium by bombarding californium-252 with boron ions?
- Why did the synthesis of lawrencium mark the closing of the actinide series and the 5f block of the periodic table?
- How does the nuclear shell model apply to the modern search for superheavy elements?
- What happens chemically when polyacetylene is 'doped' with iodine vapour?
- How did Theodore Gray turn the phrase 'periodic table' into an actual piece of furniture?
- Why did radioactive and gaseous elements pose particular challenges for Gray's element collection?