.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "api/gallery/structure/periodic_table/plot_01_mendeleev_periodic_table.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_api_gallery_structure_periodic_table_plot_01_mendeleev_periodic_table.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_api_gallery_structure_periodic_table_plot_01_mendeleev_periodic_table.py:


Mendeleev's periodic table: periodicity and the atomic-weight inversions
========================================================================

Mendeleev ordered the elements by atomic weight but let chemical
behavior overrule the order where the two disagreed. Most famously he
placed tellurium (127.6) before iodine (126.9) so that iodine fell with
the halogens. Moseley later showed that the true ordering quantity is
the atomic number :math:`Z`. Left: the standard atomic weights of all 118
elements in :data:`chemistrykit.periodic_table.PERIODIC_TABLE` against
:math:`Z`. The points where weight *decreases* as :math:`Z` increases are
exactly the "inversions" an atomic-weight ordering gets wrong. Ar/K,
Co/Ni and Te/I are the chemically real ones; those past uranium reflect
only the convention of listing the longest-lived isotope's mass number
for elements with no stable isotope. Right: the
periodicity itself, Pauling electronegativity rising across each period
and collapsing at each alkali metal.

.. GENERATED FROM PYTHON SOURCE LINES 21-51

.. code-block:: Python

    import matplotlib.pyplot as plt
    import numpy as np

    from chemistrykit.periodic_table import PAULING_ELECTRONEGATIVITY, PERIODIC_TABLE_BY_NUMBER, molar_mass

    Z = np.arange(1, 119)
    mass = np.array([PERIODIC_TABLE_BY_NUMBER[z].atomic_mass for z in Z])
    inversions = [z for z in Z[:-1] if mass[z] < mass[z - 1]]

    fig, axes = plt.subplots(1, 2, figsize=(12, 4.8))
    axes[0].plot(Z, mass, ".", color="steelblue")
    for z in inversions:
        a, b = PERIODIC_TABLE_BY_NUMBER[z], PERIODIC_TABLE_BY_NUMBER[z + 1]
        axes[0].plot([z, z + 1], [a.atomic_mass, b.atomic_mass], "o-", color="firebrick")
        if z < 90:  # past U the "weights" are isotope mass numbers
            axes[0].annotate(f"{a.symbol}/{b.symbol}", (z, a.atomic_mass), textcoords="offset points", xytext=(-30, 8))
    axes[0].set_xlabel("atomic number Z")
    axes[0].set_ylabel("standard atomic weight (u)")
    axes[0].set_title("Atomic weight vs. Z: inversions in red")

    en = [(z, PAULING_ELECTRONEGATIVITY[PERIODIC_TABLE_BY_NUMBER[z].symbol]) for z in Z if PERIODIC_TABLE_BY_NUMBER[z].symbol in PAULING_ELECTRONEGATIVITY]
    zs, chis = np.array(en).T
    axes[1].plot(zs, chis, "o-", color="darkorange", markersize=3)
    for alkali in (3, 11, 19, 37, 55, 87):
        axes[1].axvline(alkali, color="gray", linewidth=0.6)
    axes[1].set_xlabel("atomic number Z")
    axes[1].set_ylabel("Pauling electronegativity")
    axes[1].set_title("Periodicity: each period starts at an alkali metal (lines)")
    fig.tight_layout()




.. image-sg:: /api/gallery/structure/periodic_table/images/sphx_glr_plot_01_mendeleev_periodic_table_001.png
   :alt: Atomic weight vs. Z: inversions in red, Periodicity: each period starts at an alkali metal (lines)
   :srcset: /api/gallery/structure/periodic_table/images/sphx_glr_plot_01_mendeleev_periodic_table_001.png
   :class: sphx-glr-single-img





.. GENERATED FROM PYTHON SOURCE LINES 52-54

.. code-block:: Python

    print("inversions:", ", ".join(f"{PERIODIC_TABLE_BY_NUMBER[z].symbol}/{PERIODIC_TABLE_BY_NUMBER[z + 1].symbol}" for z in inversions))





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    inversions: Ar/K, Co/Ni, Te/I, Th/Pa, U/Np, Pu/Am, Bh/Hs




.. GENERATED FROM PYTHON SOURCE LINES 55-57

With the full table, molar masses of heavy-element compounds come
straight from their formulas:

.. GENERATED FROM PYTHON SOURCE LINES 57-62

.. code-block:: Python


    for f in ("UF6", "K2[PtCl6]", "HgCl2", "Gd2O3", "Pb(NO3)2"):
        print(f"{f:10s} {molar_mass(f):8.2f} g/mol")

    plt.show()




.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    UF6          352.02 g/mol
    K2[PtCl6]    485.98 g/mol
    HgCl2        271.49 g/mol
    Gd2O3        362.50 g/mol
    Pb(NO3)2     331.21 g/mol





.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.123 seconds)


.. _sphx_glr_download_api_gallery_structure_periodic_table_plot_01_mendeleev_periodic_table.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: plot_01_mendeleev_periodic_table.ipynb <plot_01_mendeleev_periodic_table.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: plot_01_mendeleev_periodic_table.py <plot_01_mendeleev_periodic_table.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: plot_01_mendeleev_periodic_table.zip <plot_01_mendeleev_periodic_table.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_