Как зная массу найти элемент

1. 

   An element is defined by the number of protons in one atom. For example, every single atom of hydrogen has exactly one proton. We say that hydrogen has a proton number or atomic number of 1.^[1]
   The periodic table is arranged in order of proton number, which is why hydrogen is in the very first box with a 1 next to it.

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   The total electron count equals the atomic number. In a neutral atom, the number of electrons is exactly equal to the number of protons. This number is the atomic number of the element, which you can look up on the periodic table. If you are a little further in your chemistry studies, you might be given an electron configuration to read. All of the superscript numbers (^{like this}) are electron counts, so add all these together to find the total number of electrons.^[2]
   

1. 

   Memorize the periodic table structure to read electron configurations quickly. The structure of the periodic table is closely related to how electron orbitals are filled. With a little practice you can jump directly to the right region of the periodic table.^[4]
   Note that the electron configuration must be in its ground state for this to work.

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1. 

   Compare the spectra to the known spectra of elements. In spectroscopy, scientists examine how light interacts with an unknown material. Each element releases a unique pattern of light, which you can see on the spectroscopy results, called «spectra».^[6]
   

   • For example, a lithium spectrum has a very bright, thick green line, and several other fainter ones in different colors. If your spectrum has all those same lines on it, the light came from the element lithium.^[7]
     (Some types of spectra will show dark gaps instead of bright lines, but you can compare these the same way.)
   • Want to know why this works? Electrons only absorb and emit light at very specific wavelengths (meaning specific colors). Different elements have different arrangements of electrons, which leads to different colors of bands.^[8]
     
   • A more advanced spectroscope shows a detailed graph instead of a few lines. You can match the x-axis value at each peak to a table of known values to identify molecules. As you learn about different types of molecules, you’ll learn to focus on just a few useful spots on the graph to save time.^[9]
     

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   Look for elements whose atomic masses match the graph. A mass spectrometer sorts the components of a sample by mass. To read the bar graph showing the results, check the «m/z» axis for the values of the taller bars. Some values will match the atomic mass of an element that was part of the sample. Others (usually the larger ones) represent compounds, so that mass will equal the sum of masses of multiple atoms.^[10]
   

   • Let’s say the tallest bar is at m/z 18, with short bars at 1, 16, and 17. Only two of these match the atomic mass of an element: hydrogen (atomic mass 1) and oxygen (atomic mass 16). Adding these atoms together gives you the compounds HO (mass 1 + 16 = 17) and H₂O (mass 1 + 1 + 16 = 18). This sample was water!^[11]
     
   • Technically, a mass spectrometer ionizes the sample and sorts by the ratio of mass to charge (or m/z). But most ions will have a charge of 1, and so you can ignore the division problem and just look at mass. The smallest bars often represent small amounts of more charged particles that you can ignore for identification purposes.^[12]
     

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• Mass spectrometer readings get complicated when you sample large molecules that can break into many parts.^[13]
  If you can narrow down the sample to a few possibilities, you can look up the mass spectra of each one and compare that to your actual results.

• Electron configurations can also be written in noble gas notation, which uses a noble gas element symbol to stand in for that element’s electron shell.^[14]
  For instance, can be expanded with neon’s electron configuration into . To identify the element by electron count, add the electrons in the expanded configuration.^[15]
  In this case there are 2+2+6+2+4 = 16 electrons, so this must be the sixteenth element, sulfur.

• Most periodic tables show two numbers next to each element. The smaller one (that always goes up by 1 as you go left to right) is the atomic number or proton number. The larger number is the atomic mass.

• If you are given an electron configuration in an excited state, you can’t use the highest energy electron to identify the element. Identify the ground state for that number of electrons first.

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