Final answer:
The numbers of protons and electrons in atoms are used to place elements in the modern periodic table by organizing elements based on their atomic number and electron configuration.
Step-by-step explanation:
The number of protons in an atom is determined by its atomic number, which is unique to each element. Mendeleev's periodic table was organized based on the atomic number of elements. In the modern periodic table, elements are arranged in order of increasing atomic number, which reflects the number of protons in the nucleus.
The number of electrons in an atom is usually equal to the number of protons, ensuring the atom is electrically neutral. However, in ions, the number of electrons can vary. When placing elements in the periodic table, the arrangement takes into account the electron configuration and the patterns in the outermost electron shell.
By considering both the number of protons and electrons, the modern periodic table accurately groups elements based on their atomic properties and chemical behavior.
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