Jun 18, Their atomic masses are the 'wrong way round'. Explanation: If you look at Iodine and Tellurium on the modern periodic table, you will find their atomic number increases Te is 52, I is 53 but their atomic mass decreases Te is , I is To put Te and I in the correct sequence Mendeleev looked at their properties. Related questions How can the periodic table be used to predict new elements?
How are the elements are organized in the periodic table? Individual pieces of information take on broader significance when put together with other parts of the puzzle. When Mendeleev put his periodic table together, nobody knew about the existence of the nucleus. It was not until that Rutherford conducted his gold foil experiment that demonstrated the presence of the nucleus in the atom.
Just two years later, in , English physicist Henry Moseley examined x-ray spectra of a number of chemical elements.
He would shoot x-rays through crystals of the element and study the wavelengths of the radiation that he detected. Moseley found that there was a relationship between wavelength and atomic number. His results led to the definition of atomic number as the number of protons contained in the nucleus of each atom. To make his classification work Mendeleev made a few changes to his order:. Mendeleev left gaps in his table to place elements not known at the time.
By looking at the chemical properties and physical properties of the elements next to a gap, he could also predict the properties of these undiscovered elements. For example, Mendeleev predicted the existence of 'eka-silicon', which would fit into a gap next to silicon. The element germanium was discovered later. Its properties were found to be similar to the predicted ones and confirmed Mendeleev's periodic table.
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