question: how does chesmists of 1700s - 1900s knows how many protons the elements have?
comment: They didn't. It was only in the early years of the 20th century that Rutherford showed that there was a small positively charged nucleus at the centre of an atom. That led to the development of modern pictures of the atom. That doesn't mean that clues were there. In the 18th century, Lavoisier and others had measured the masses of different elements that reacted together and found that there were fixed ratios and simple multiples. That led to valence and ideas of atomic weights. In turn that led to ordering the elements by mass and a number of tables to try and make sense of the data. Ultimately Mendeleev's Periodic Table of 1869 and atomic physics discoveries from then on made sense of atomic structure and behaviour.
passages: The history of mass spectrometry has its roots in physical and chemical studies regarding the nature of matter. The study of gas discharges in the mid 19th century led to the discovery of anode and cathode rays, which turned out to be positive ions and electrons. Improved capabilities in the separation of these positive ions enabled the discovery of stable isotopes of the elements. The first such discovery was with the element neon, which was shown by mass spectrometry to have at least two stable isotopes: Ne (neon with 10 protons and 10 neutrons) and Ne (neon with 10 protons and 12 neutrons). Mass spectrometers were used in the Manhattan Project for the separation of isotopes of uranium necessary to create the atomic bomb.
   Prior to 2010, the proton radius was measured using one of two methods: one relying on spectroscopy, and one relying on nuclear scattering.
  
  Section::::Problem.:Spectroscopy method.
   BULLET::::- IX. — Aleksandr Vinogradov — 24 February 1955 — "Isotopes of lead"
  
  BULLET::::- X. — — 9 February 1956 — "Status of trace elements in liquid and solid phases"
  
  BULLET::::- XI. — — 7 February 1957. — "Individual chemical elements and complexing"
  
  BULLET::::- XII. — Nikolai Semenov — 27 February 1958 — "On some chain reactions"
  
  BULLET::::- XIII. — Stepan Danilov — 12 February 1959 — "The Origin of simultaneous oxidation-reduction of organic substances"
   In 1932, Kenneth Bainbridge developed a mass spectrometer with a resolving power of 600 and a relative precision of one part in 10,000. He used this instrument to verify the equivalence of mass and energy, E = mc.
  
  Section::::Manhattan Project.
   By 1934 groups led by Stern, now in Pittsburgh, and I. I. Rabi in New York had independently measured the magnetic moments of the proton and deuteron. 
   Finally, Geiger and Marsden tested how the scattering varied with the velocity of the alpha particles (i.e. if "s ∝ 1/v"). Using the same apparatus again, they slowed the alpha particles by placing extra sheets of mica in front of the alpha particle source. They found that, within the range of experimental error, that the number of scinitillations was indeed proportional to "1/v".
  
  Section::::Timeline.:Rutherford determines the nucleus is positively charged.
   BULLET::::- Immediately after that gap, he left a further gap, predicting another metal, dark grey in colour.
  
  So, for Mendeleev to be vindicated, the gaps needed to be filled, and luckily, in 1859, new instrumentation had been developed for discovering elements.
  
  Section::::Episode 2: The Order of the Elements.:Bunsen's burner and Kirchhoff's spectrometer.
  
  Robert Bunsen knew that when certain elements burned in the flames of his burner they each turned the flame a different colour. Copper burned green, strontium red and potassium lilac – Bunsen wondered if every element had a unique colour.
   BULLET::::- 1925: Mexican-American botanist Ynes Mexia embarked on her first botanical expedition into Mexico, collecting over 1500 plant specimens. Over the course of the next thirteen years, Mexia collected more than 145,000 specimens from Mexico, Alaska, and multiple South American countries. She discovered 500 new species.
  
  BULLET::::- 1925: American medical scientist Florence Sabin became the first woman elected to the National Academy of Science.
  
  BULLET::::- 1925: British-American astronomer and astrophysicist Cecilia Payne-Gaposchkin established that hydrogen is the most common element in stars, and thus the most abundant element in the universe.
   Canal rays, also called anode rays, were observed by Eugen Goldstein, in 1886. Goldstein used a gas discharge tube which had a perforated cathode. The rays are produced in the holes (canals) in the cathode and travels in a direction opposite to the "cathode rays," which are streams of electrons. Goldstein called these positive rays "Kanalstrahlen" - canal rays. In 1907 a study of how this "ray" was deflected in a magnetic field, revealed that the particles making up the ray were not all the same mass.
  
  Section::::Discovery of isotopes.
   Initial versions of the periodic table did not distinguish rare earth elements from transition elements, helping to explain both why Mendeleev's predictions for heavier unknown elements did not fare as well as those for the lighter ones and why they are not as well known or documented.
  
  Scandium oxide was isolated in late 1879 by Lars Fredrick Nilson; Per Teodor Cleve recognized the correspondence and notified Mendeleev late in that year. Mendeleev had predicted an atomic mass of 44 for ekaboron in 1871, while scandium has an atomic mass of 44.955908.
   The nuclear method is similar to Rutherford's scattering experiments that established the existence of the nucleus. Small particles such as electrons can be fired at a proton, and by measuring how the electrons are scattered, the size of the proton can be inferred. Consistent with the spectroscopy method, this produces a proton radius of about (or ), .
  
  Section::::Problem.:2010 experiment.
   Section::::Canal rays.
  
  In the mid-nineteenth century, Julius Plücker investigated the light emitted in discharge tubes and the influence of magnetic fields on the glow. Later, in 1869, Johann Wilhelm Hittorf studied discharge tubes with energy rays extending from a negative electrode, the cathode. These rays produced a fluorescence when they hit a tube's glass walls, and when interrupted by a solid object they cast a shadow.
   Closely connected with terrestrial magnetism, and to be considered with it, is the Aurora Borealis. In the week that covered the end of August and the beginning of September, 1859, there occurred an exceedingly brilliant display of the Northern Lights. Believing that an exhaustive discussion of a single aurora promised to do more for the promotion of science than an imperfect study of an indefinite number of them, Professor Loomis undertook at once to collect and to collate accounts of this display. A large number of such accounts were secured from North America, from Europe, from Asia, and from places in the Southern Hemisphere; especially all the reports from the Smithsonian observers and correspondents, were placed in his hands by the Secretary, Professor Henry.
   PPMs were once widely used in mineral exploration. They have largely been superseded by Overhauser effect magnetometers and alkali vapour (cesium, rubidium, potassium) or helium magnetometers, which sample faster and are more sensitive.
  
  Section::::Principles of operation.
   The systematic attribution of spectra to chemical elements began in the 1860s with the work of German physicist [[Gustav Kirchhoff]] and chemist [[Robert Bunsen]]. Bunsen and Kirchhoff applied the optical techniques of Fraunhofer, Bunsen's [[Bunsen burner|improved flame source]] and a highly systematic experimental procedure to a detailed examination of the spectra of chemical compounds. They established the linkage between [[chemical element]]s and their unique spectral patterns. In the process, they established the technique of analytical spectroscopy. In 1860, they published their findings on the spectra of eight elements and identified these elements' presence in several natural compounds.
   Mendeleev's genius was to combine those two methods together. However, the odds were stacked against him – little more than half the known elements had been discovered: he was playing with an incomplete deck of cards.
  
  He stayed up for three days and nights then, finally, on 17 February 1869, he fell asleep and dreamt of all 63 known elements laid out in a grand table.
  
  Mendeleev's table reveals the relationship between all the elements in their order:
  
  BULLET::::- Atomic weights increase reading from left to right;
  
  BULLET::::- Triads and Octaves are visible reading down the columns.
   His work on isotopes also led to his formulation of the Whole Number Rule which states that "the mass of the oxygen isotope being defined [as 16], all the other isotopes have masses that are very nearly whole numbers," a rule that was used extensively in the development of nuclear energy. The exact mass of many isotopes was measured leading to the result that hydrogen has a 1% higher mass than expected by the average mass of the other elements. Aston speculated about the subatomic energy and the use of it in 1936.
   Section::::Career and research.:Isotopes and mass spectrometry.
   A significant challenge facing 19th-century organic chemists was the lack of instruments and methods of analysis to support accurate, replicable analyses of organic materials. Many chemists worked on the problem of organic analysis, including French Joseph Louis Gay-Lussac and Swedish Jöns Jacob Berzelius, before Liebig developed his version of an apparatus for determining the carbon, hydrogen, and oxygen content of organic substances in 1830. It involved an ingenious array of five glass bulbs, called a "Kaliapparat" to trap the oxidation product of the carbon in the sample, following combustion of the sample. Before reaching the "Kaliapparat", the combustion gases were conducted through a tube of hygroscopic calcium chloride, which absorbed and retained the oxidation product of the hydrogen of the sample, namely water vapor. Next, in the "Kaliapparat", carbon dioxide was absorbed in a potassium hydroxide solution in the three lower bulbs, and used to measure the weight of carbon in the sample. For any substance consisting only of carbon, hydrogen, and oxygen, the percentage of oxygen was found by subtracting the carbon and hydrogen percentages from 100%; the remainder must be the percentage of oxygen. A charcoal furnace (a sheet-steel tray in which the combustion tube was laid) was used for the combustion. Weighing carbon and hydrogen directly, rather than estimating them volumetrically, greatly increased the method's accuracy of measurement. Liebig's assistant Carl Ettling perfected glass-blowing techniques for producing the "Kaliapparat", and demonstrated them to visitors. Liebig's kaliapparat simplified the technique of quantitative organic analysis and rendered it routine. Brock suggests that the availability of a superior technical apparatus was one reason why Liebig was able to attract so many students to his laboratory. His method of combustion analysis was used pharmaceutically, and certainly made possible many contributions to organic, agricultural and biological chemistry.
   In 1958 Glenn A. Black and Eli Lilly, following the work of M. J. Aitken and his associates at the Oxford University (UK) Archaeometric Laboratory, used proton magnetometers to locate and map buried archaeological features, including iron objects in the soil, thermoremanent magnetization of fired clays, and differences in the magnetic susceptibility of disturbed soils. During 1961–1963, they surveyed more than of the Angel Mounds State Historic Site in Indiana and excavated more than to match anomalous magnetometer readings with the archaeological features that produced them. This was the first systematic use of a proton magnetometer for archaeological research in North America.
   Section::::Prout's Hypothesis.
   His anonymous obituarist in "The Mariner's Mirror" wrote of him that "it has been said that Bonner-Smith not only knew every one of the 100,000 books in the library, but was also familiar with all their contents. It is a fact that he could immediately direct students and enquirers to whatever references were needed, and have the necessary books at once placed before them, Scores of our members must owe a great debt of gratitude to his ever-ready and encyclopaedic acquaintance with books and documents dealing with the sea and the services."
   Section::::Early observations.:Nuclide abundances.
  
  Determination of the cosmic abundance of elements has a history dating back to early spectroscopic measurements of light from astronomical objects and the identification of emission and absorption lines which corresponded to particular electronic transitions in chemical elements identified on Earth. For example, the element Helium was first identified through its spectroscopic signature in the Sun before it was isolated as a gas on Earth.
  
  Computing relative abundances was achieved through corresponding spectroscopic observations to measurements of the elemental composition of meteorites.
  
  Section::::Early observations.:Detection of the cosmic microwave background.
   Section::::Career.
  
  In the summer of 1924, Meissner became a First Assistant at the Physics Institute of the University of Zurich. Here he studied the spectra of indium, gallium, neon, argon, and caesium, the arc spectrum of lead (spectrum of neutral or non-ionized lead), the Stark effect of neon, and general problems of detecting radiation.
   In 1854 and 1855, [[David Alter]] published observations on the spectra of metals and gases, including an independent observation of the [[Balmer lines]] of hydrogen.
  
  [[Image:Kirchhoffs first spectroscope.jpg|thumb|Spectroscope of Kirchhoff and Bunsen]]
  
presuppositions: Chemists of the 1700s - 1900s knew how many protons elements have. Chemists of the 1700s to the 1900s knew how many protons the elements have.
corrections: Chemists of the 1700s - 1900s did not know how many protons elements have. Chemists didn't know how many protons the elements have until the early years of the 20th century.
raw_presuppositions: Chemists of the 1700s - 1900s knew how many protons elements have. Chemists of the 1700s to the 1900s knew how many protons the elements have.
raw_corrections: Chemists of the 1700s - 1900s did not know how many protons elements have. Chemists didn't know how many protons the elements have until the early years of the 20th century.