In the modern periodic table, Mg and Ca are the last pair of elects for which Newlands' Law of Octaves would hold true.
Law of Octaves is the generalization that was made by Newlands. It states that when chemical elements are arranged based on their increasing atomic weight, then the ones that have the same chemical and physical properties will occur after an interval of seven elements.
In such a case, every eighth element will have identical properties when the elements in the periodic table are arranged based on their atomic masses.
Based on the above information, Magnesium (Mg) has an atomic number of 12 while Calcium (Ca) has an atomic number of 20. Therefore, the elements follow the law of Octaves as they have a difference of 8 in their atomic numbers.
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