How did Dmitri Mendeleev arrange the elements in the periodic table?

Answer 1

Mendeleev ordered the elements from lowest Atomic Mass unit (amu) to highest atomic mass unit.

Answer 2

Dmitri Mendeleev arranged the elements in the Periodic Table based on their atomic weight and chemical properties. He left gaps for elements that had not been discovered yet, predicting their properties with remarkable accuracy. This arrangement allowed him to predict the properties of unknown elements and led to the development of the modern periodic table.

Answer 3

He lined them up according to their properties and other characteristics.

First, John Newlands looked at the atomic masses of the known elements. He noticed that elements with similar physical and chemical properties came in intervals of 8. (So the 1st, 8th and 15th element were similar.) He proposed this idea as a unifying principle of chemistry. But it didn't work very well - not all the elements matched up.

Mendeleev's contribution was to suggest that not all elements had been discovered yet. This was reasonable, because in those days a lot of new elements were being discovered. He rearranged the table so that it had gaps where he believed missing elements were. In fact, he was even confident enough to predict the properties of the missing elements. The risk paid off: Many of his predictions were uncannily accurate.

Since then there have been a few modifications. The missing elements have been discovered, as well as a whole new group not in Mendeleev's table (the noble gases). The lanthanides and actinides have been moved into their own part to save space. And it is now understood that the important number is not mass number but atomic number (in Mendeleev's time this distinction was not appreciated, since neutrons had not been discovered). But, on the whole, the table is the same today as it was when Mendeleev produced it.

We also have an understanding of why it is that this pattern exists. It is due to the number of electrons in the outer shell of electrons, as each group has a different number in its outer shell (for example, Sodium [Na] in group 1 has 1 electron in its outer shell while Oxygen [O] has 6 electrons in the outer shell). These also effect their reactivity and thus their characteristics (as mentioned before) due to the stability of different groups.

Answer 4

Mendeleev placed the known elements in order of increasing atomic mass. He then grouped the elements based on similar chemical properties. In this way, he was able to notice gaps in the table where unknown elements should be and to predict their chemical properties.

Answer 5

Mendeleev had written the properties of elements on pieces of card and tradition has it that after organising the cards while playing patience he suddenly realised that by arranging the element cards in order of increasing atomic weight that certain types of element regularly occurred. For example a reactive non-metal was directly followed by a very reactive light metal, then a less reactive light metal. The image of a stamp collectors' miniature sheet shows a stamp commemorating the hundredth anniversary of the Periodic Table superimposed on some of Mendeleev's original jottings.

Answer 6

After becoming a teacher, he wrote the definitive two-volume textbook at that time: Principles of Chemistry (1868-1870). As he attempted to classify the elements according to their chemical properties, he noticed patterns that led him to postulate his Periodic Table.

Unknown to Mendeleev, several other scientists had also been working on their own table of elements. One was John Newlands, who published his Law of Octaves in 1865. However, the lack of spaces for undiscovered elements and the placing of two elements in one box were criticized and his ideas were not accepted. Another was Lothar Meyer, who published a work in 1864, describing 28 elements. Like Newlands, Meyer did not seem to have the idea of using a table to predict new elements.

Mendeleev began by making for himself the following table:

Cl 35.5 | K 39 | Ca 40

Br 80 | Rb 85 | Sr 88

I 127 | Cs 133 | Ba 137

And by adding additional elements following this pattern, he developed his version of the periodic table.

Answer 7

Dimitri Mendeleev arranged his elements in order of increasing atomic mass.

Answer 8

He arranged the various elements in the increasing order of their atomic masses and repeating properties.

Answer 9

He arranged the elements in the increasing order of their atomic masses.

Answer 10

Dmitri Mendeleev organized chemical elements in rows and columns in a table; he proposed the law of the characteristics periodicity for chemical elements.